diff --git a/mercurial/debugcommands.py b/mercurial/debugcommands.py
--- a/mercurial/debugcommands.py
+++ b/mercurial/debugcommands.py
@@ -28,7 +28,6 @@
 from .node import (
     bin,
     hex,
-    nullhex,
     nullid,
     nullrev,
     short,
@@ -1944,120 +1943,84 @@
         )
 
 
-@command(b'debugmergestate', [], b'')
-def debugmergestate(ui, repo, *args):
+@command(b'debugmergestate', [] + cmdutil.templateopts, b'')
+def debugmergestate(ui, repo, *args, **opts):
     """print merge state
 
     Use --verbose to print out information about whether v1 or v2 merge state
     was chosen."""
 
-    def _hashornull(h):
-        if h == nullhex:
-            return b'null'
-        else:
-            return h
-
-    def printrecords(version):
-        ui.writenoi18n(b'* version %d records\n' % version)
-        if version == 1:
-            records = v1records
+    if ui.verbose:
+        ms = mergemod.mergestate(repo)
+
+        # sort so that reasonable information is on top
+        v1records = ms._readrecordsv1()
+        v2records = ms._readrecordsv2()
+
+        if not v1records and not v2records:
+            pass
+        elif not v2records:
+            ui.writenoi18n(b'no version 2 merge state\n')
+        elif ms._v1v2match(v1records, v2records):
+            ui.writenoi18n(b'v1 and v2 states match: using v2\n')
         else:
-            records = v2records
-
-        for rtype, record in records:
-            # pretty print some record types
-            if rtype == b'L':
-                ui.writenoi18n(b'local: %s\n' % record)
-            elif rtype == b'O':
-                ui.writenoi18n(b'other: %s\n' % record)
-            elif rtype == b'm':
-                driver, mdstate = record.split(b'\0', 1)
-                ui.writenoi18n(
-                    b'merge driver: %s (state "%s")\n' % (driver, mdstate)
-                )
-            elif rtype in b'FDC':
-                r = record.split(b'\0')
-                f, state, hash, lfile, afile, anode, ofile = r[0:7]
-                if version == 1:
-                    onode = b'not stored in v1 format'
-                    flags = r[7]
-                else:
-                    onode, flags = r[7:9]
-                ui.writenoi18n(
-                    b'file: %s (record type "%s", state "%s", hash %s)\n'
-                    % (f, rtype, state, _hashornull(hash))
-                )
-                ui.writenoi18n(
-                    b'  local path: %s (flags "%s")\n' % (lfile, flags)
-                )
-                ui.writenoi18n(
-                    b'  ancestor path: %s (node %s)\n'
-                    % (afile, _hashornull(anode))
-                )
-                ui.writenoi18n(
-                    b'  other path: %s (node %s)\n'
-                    % (ofile, _hashornull(onode))
-                )
-            elif rtype == b'f':
-                filename, rawextras = record.split(b'\0', 1)
-                extras = rawextras.split(b'\0')
-                i = 0
-                extrastrings = []
-                while i < len(extras):
-                    extrastrings.append(b'%s = %s' % (extras[i], extras[i + 1]))
-                    i += 2
-
-                ui.writenoi18n(
-                    b'file extras: %s (%s)\n'
-                    % (filename, b', '.join(extrastrings))
-                )
-            elif rtype == b'l':
-                labels = record.split(b'\0', 2)
-                labels = [l for l in labels if len(l) > 0]
-                ui.writenoi18n(b'labels:\n')
-                ui.write((b'  local: %s\n' % labels[0]))
-                ui.write((b'  other: %s\n' % labels[1]))
-                if len(labels) > 2:
-                    ui.write((b'  base:  %s\n' % labels[2]))
-            else:
-                ui.writenoi18n(
-                    b'unrecognized entry: %s\t%s\n'
-                    % (rtype, record.replace(b'\0', b'\t'))
-                )
-
-    # Avoid mergestate.read() since it may raise an exception for unsupported
-    # merge state records. We shouldn't be doing this, but this is OK since this
-    # command is pretty low-level.
-    ms = mergemod.mergestate(repo)
-
-    # sort so that reasonable information is on top
-    v1records = ms._readrecordsv1()
-    v2records = ms._readrecordsv2()
-    order = b'LOml'
-
-    def key(r):
-        idx = order.find(r[0])
-        if idx == -1:
-            return (1, r[1])
-        else:
-            return (0, idx)
-
-    v1records.sort(key=key)
-    v2records.sort(key=key)
-
-    if not v1records and not v2records:
-        ui.writenoi18n(b'no merge state found\n')
-    elif not v2records:
-        ui.notenoi18n(b'no version 2 merge state\n')
-        printrecords(1)
-    elif ms._v1v2match(v1records, v2records):
-        ui.notenoi18n(b'v1 and v2 states match: using v2\n')
-        printrecords(2)
-    else:
-        ui.notenoi18n(b'v1 and v2 states mismatch: using v1\n')
-        printrecords(1)
-        if ui.verbose:
-            printrecords(2)
+            ui.writenoi18n(b'v1 and v2 states mismatch: using v1\n')
+
+    opts = pycompat.byteskwargs(opts)
+    if not opts[b'template']:
+        opts[b'template'] = (
+            b'{if(commits, "", "no merge state found\n")}'
+            b'{commits % "{name}{if(label, " ({label})")}: {node}\n"}'
+            b'{files % "file: {path} (state \\"{state}\\")\n'
+            b'  local path: {local_path} (flags \\"{local_flags}\\")\n'
+            b'  ancestor path: {ancestor_path} (node {ancestor_node})\n'
+            b'  other path: {other_path} (node {other_node})\n'
+            b'{extras % "  extra: {key} = {value}\n"}'
+            b'"}'
+        )
+
+    ms = mergemod.mergestate.read(repo)
+
+    fm = ui.formatter(b'debugmergestate', opts)
+    fm.startitem()
+
+    fm_commits = fm.nested(b'commits')
+    if ms.active():
+        for name, node, label_index in (
+            (b'local', ms.local, 0),
+            (b'other', ms.other, 1),
+        ):
+            fm_commits.startitem()
+            fm_commits.data(name=name)
+            fm_commits.data(node=hex(node))
+            if ms._labels and len(ms._labels) > label_index:
+                fm_commits.data(label=ms._labels[label_index])
+    fm_commits.end()
+
+    fm_files = fm.nested(b'files')
+    if ms.active():
+        for f in ms:
+            fm_files.startitem()
+            fm_files.data(path=f)
+            state = ms._state[f]
+            fm_files.data(state=state[0])
+            fm_files.data(local_key=state[1])
+            fm_files.data(local_path=state[2])
+            fm_files.data(ancestor_path=state[3])
+            fm_files.data(ancestor_node=state[4])
+            fm_files.data(other_path=state[5])
+            fm_files.data(other_node=state[6])
+            fm_files.data(local_flags=state[7])
+            fm_extras = fm_files.nested(b'extras')
+            for k, v in ms.extras(f).items():
+                fm_extras.startitem()
+                fm_extras.data(key=k)
+                fm_extras.data(value=v)
+            fm_extras.end()
+
+    fm_files.end()
+
+    fm.end()
 
 
 @command(b'debugnamecomplete', [], _(b'NAME...'))
diff --git a/relnotes/next b/relnotes/next
--- a/relnotes/next
+++ b/relnotes/next
@@ -12,6 +12,9 @@
    commits that are being merged, when there are conflicts. Also works
    for conflicts caused by e.g. `hg graft`.
 
+ * `hg debugmergestate` output is now templated, which may be useful
+   e.g. for IDEs that want to help the user resolve merge conflicts.
+
 
 == New Experimental Features ==
 
@@ -26,6 +29,9 @@
    can use the new `conflictparents()` revset for finding the other
    parent during a conflict.
 
+ * `hg debugmergestate` output format changed. Let us know if that is
+   causing you problems and we'll roll it back.
+
 
 == Internal API Changes ==
 
diff --git a/tests/test-backout.t b/tests/test-backout.t
--- a/tests/test-backout.t
+++ b/tests/test-backout.t
@@ -710,22 +710,21 @@
   [1]
   $ hg status
   $ hg debugmergestate
-  * version 2 records
   local: b71750c4b0fdf719734971e3ef90dbeab5919a2d
   other: a30dd8addae3ce71b8667868478542bc417439e6
-  file extras: foo (ancestorlinknode = 91360952243723bd5b1138d5f26bd8c8564cb553)
-  file: foo (record type "F", state "u", hash 0beec7b5ea3f0fdbc95d0dd47f3c5bc275da8a33)
+  file: foo (state "u")
     local path: foo (flags "")
     ancestor path: foo (node f89532f44c247a0e993d63e3a734dd781ab04708)
     other path: foo (node f50039b486d6fa1a90ae51778388cad161f425ee)
+    extra: ancestorlinknode = 91360952243723bd5b1138d5f26bd8c8564cb553
   $ mv .hg/merge/state2 .hg/merge/state2-moved
   $ hg debugmergestate
-  * version 1 records
   local: b71750c4b0fdf719734971e3ef90dbeab5919a2d
-  file: foo (record type "F", state "u", hash 0beec7b5ea3f0fdbc95d0dd47f3c5bc275da8a33)
+  other: b71750c4b0fdf719734971e3ef90dbeab5919a2d
+  file: foo (state "u")
     local path: foo (flags "")
     ancestor path: foo (node f89532f44c247a0e993d63e3a734dd781ab04708)
-    other path: foo (node not stored in v1 format)
+    other path:  (node foo)
   $ mv .hg/merge/state2-moved .hg/merge/state2
   $ hg resolve -l  # still unresolved
   U foo
diff --git a/tests/test-completion.t b/tests/test-completion.t
--- a/tests/test-completion.t
+++ b/tests/test-completion.t
@@ -289,7 +289,7 @@
   debuglabelcomplete: 
   debuglocks: force-lock, force-wlock, set-lock, set-wlock
   debugmanifestfulltextcache: clear, add
-  debugmergestate: 
+  debugmergestate: style, template
   debugnamecomplete: 
   debugnodemap: dump-new, dump-disk, check, metadata
   debugobsolete: flags, record-parents, rev, exclusive, index, delete, date, user, template
diff --git a/tests/test-histedit-non-commute-abort.t b/tests/test-histedit-non-commute-abort.t
--- a/tests/test-histedit-non-commute-abort.t
+++ b/tests/test-histedit-non-commute-abort.t
@@ -77,36 +77,22 @@
 insert unsupported advisory merge record
   $ hg --config extensions.fakemergerecord=$TESTDIR/fakemergerecord.py fakemergerecord -x
   $ hg debugmergestate
-  * version 2 records
-  local: 8f7551c7e4a2f2efe0bc8c741baf7f227d65d758
-  other: e860deea161a2f77de56603b340ebbb4536308ae
-  labels:
-    local: local
-    other: histedit
-  unrecognized entry: x	advisory record
-  file extras: e (ancestorlinknode = 0000000000000000000000000000000000000000)
-  file: e (record type "F", state "u", hash 58e6b3a414a1e090dfc6029add0f3555ccba127f)
+  local (local): 8f7551c7e4a2f2efe0bc8c741baf7f227d65d758
+  other (histedit): e860deea161a2f77de56603b340ebbb4536308ae
+  file: e (state "u")
     local path: e (flags "")
-    ancestor path: e (node null)
+    ancestor path: e (node 0000000000000000000000000000000000000000)
     other path: e (node 6b67ccefd5ce6de77e7ead4f5292843a0255329f)
+    extra: ancestorlinknode = 0000000000000000000000000000000000000000
   $ hg resolve -l
   U e
 
 insert unsupported mandatory merge record
   $ hg --config extensions.fakemergerecord=$TESTDIR/fakemergerecord.py fakemergerecord -X
   $ hg debugmergestate
-  * version 2 records
-  local: 8f7551c7e4a2f2efe0bc8c741baf7f227d65d758
-  other: e860deea161a2f77de56603b340ebbb4536308ae
-  labels:
-    local: local
-    other: histedit
-  file extras: e (ancestorlinknode = 0000000000000000000000000000000000000000)
-  file: e (record type "F", state "u", hash 58e6b3a414a1e090dfc6029add0f3555ccba127f)
-    local path: e (flags "")
-    ancestor path: e (node null)
-    other path: e (node 6b67ccefd5ce6de77e7ead4f5292843a0255329f)
-  unrecognized entry: X	mandatory record
+  abort: unsupported merge state records: X
+  (see https://mercurial-scm.org/wiki/MergeStateRecords for more information)
+  [255]
   $ hg resolve -l
   abort: unsupported merge state records: X
   (see https://mercurial-scm.org/wiki/MergeStateRecords for more information)
diff --git a/tests/test-merge-changedelete.t b/tests/test-merge-changedelete.t
--- a/tests/test-merge-changedelete.t
+++ b/tests/test-merge-changedelete.t
@@ -76,27 +76,23 @@
   U file2
   U file3
   --- debugmergestate ---
-  * version 2 records
-  local: 13910f48cf7bdb2a0ba6e24b4900e4fdd5739dd4
-  other: 10f9a0a634e82080907e62f075ab119cbc565ea6
-  labels:
-    local: working copy
-    other: merge rev
-  file extras: file1 (ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff)
-  file: file1 (record type "C", state "u", hash 60b27f004e454aca81b0480209cce5081ec52390)
+  local (working copy): 13910f48cf7bdb2a0ba6e24b4900e4fdd5739dd4
+  other (merge rev): 10f9a0a634e82080907e62f075ab119cbc565ea6
+  file: file1 (state "u")
     local path: file1 (flags "")
     ancestor path: file1 (node b8e02f6433738021a065f94175c7cd23db5f05be)
-    other path: file1 (node null)
-  file extras: file2 (ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff)
-  file: file2 (record type "C", state "u", hash null)
+    other path: file1 (node 0000000000000000000000000000000000000000)
+    extra: ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff
+  file: file2 (state "u")
     local path: file2 (flags "")
     ancestor path: file2 (node 5d9299349fc01ddd25d0070d149b124d8f10411e)
     other path: file2 (node e7c1328648519852e723de86c0c0525acd779257)
-  file extras: file3 (ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff)
-  file: file3 (record type "F", state "u", hash d5b0a58bc47161b1b8a831084b366f757c4f0b11)
+    extra: ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff
+  file: file3 (state "u")
     local path: file3 (flags "")
     ancestor path: file3 (node 2661d26c649684b482d10f91960cc3db683c38b4)
     other path: file3 (node a2644c43e210356772c7772a8674544a62e06beb)
+    extra: ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff
   --- file1 ---
   1
   changed
@@ -145,27 +141,23 @@
   R file2
   U file3
   --- debugmergestate ---
-  * version 2 records
-  local: 13910f48cf7bdb2a0ba6e24b4900e4fdd5739dd4
-  other: 10f9a0a634e82080907e62f075ab119cbc565ea6
-  labels:
-    local: working copy
-    other: merge rev
-  file extras: file1 (ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff)
-  file: file1 (record type "C", state "r", hash 60b27f004e454aca81b0480209cce5081ec52390)
+  local (working copy): 13910f48cf7bdb2a0ba6e24b4900e4fdd5739dd4
+  other (merge rev): 10f9a0a634e82080907e62f075ab119cbc565ea6
+  file: file1 (state "r")
     local path: file1 (flags "")
     ancestor path: file1 (node b8e02f6433738021a065f94175c7cd23db5f05be)
-    other path: file1 (node null)
-  file extras: file2 (ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff)
-  file: file2 (record type "C", state "r", hash null)
+    other path: file1 (node 0000000000000000000000000000000000000000)
+    extra: ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff
+  file: file2 (state "r")
     local path: file2 (flags "")
     ancestor path: file2 (node 5d9299349fc01ddd25d0070d149b124d8f10411e)
     other path: file2 (node e7c1328648519852e723de86c0c0525acd779257)
-  file extras: file3 (ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff)
-  file: file3 (record type "F", state "u", hash d5b0a58bc47161b1b8a831084b366f757c4f0b11)
+    extra: ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff
+  file: file3 (state "u")
     local path: file3 (flags "")
     ancestor path: file3 (node 2661d26c649684b482d10f91960cc3db683c38b4)
     other path: file3 (node a2644c43e210356772c7772a8674544a62e06beb)
+    extra: ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff
   --- file1 ---
   1
   changed
@@ -227,27 +219,23 @@
   R file2
   U file3
   --- debugmergestate ---
-  * version 2 records
-  local: 13910f48cf7bdb2a0ba6e24b4900e4fdd5739dd4
-  other: 10f9a0a634e82080907e62f075ab119cbc565ea6
-  labels:
-    local: working copy
-    other: merge rev
-  file extras: file1 (ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff)
-  file: file1 (record type "C", state "r", hash 60b27f004e454aca81b0480209cce5081ec52390)
+  local (working copy): 13910f48cf7bdb2a0ba6e24b4900e4fdd5739dd4
+  other (merge rev): 10f9a0a634e82080907e62f075ab119cbc565ea6
+  file: file1 (state "r")
     local path: file1 (flags "")
     ancestor path: file1 (node b8e02f6433738021a065f94175c7cd23db5f05be)
-    other path: file1 (node null)
-  file extras: file2 (ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff)
-  file: file2 (record type "C", state "r", hash null)
+    other path: file1 (node 0000000000000000000000000000000000000000)
+    extra: ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff
+  file: file2 (state "r")
     local path: file2 (flags "")
     ancestor path: file2 (node 5d9299349fc01ddd25d0070d149b124d8f10411e)
     other path: file2 (node e7c1328648519852e723de86c0c0525acd779257)
-  file extras: file3 (ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff)
-  file: file3 (record type "F", state "u", hash d5b0a58bc47161b1b8a831084b366f757c4f0b11)
+    extra: ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff
+  file: file3 (state "u")
     local path: file3 (flags "")
     ancestor path: file3 (node 2661d26c649684b482d10f91960cc3db683c38b4)
     other path: file3 (node a2644c43e210356772c7772a8674544a62e06beb)
+    extra: ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff
   *** file1 does not exist
   --- file2 ---
   2
@@ -293,27 +281,23 @@
   U file2
   U file3
   --- debugmergestate ---
-  * version 2 records
-  local: 13910f48cf7bdb2a0ba6e24b4900e4fdd5739dd4
-  other: 10f9a0a634e82080907e62f075ab119cbc565ea6
-  labels:
-    local: working copy
-    other: merge rev
-  file extras: file1 (ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff)
-  file: file1 (record type "C", state "r", hash 60b27f004e454aca81b0480209cce5081ec52390)
+  local (working copy): 13910f48cf7bdb2a0ba6e24b4900e4fdd5739dd4
+  other (merge rev): 10f9a0a634e82080907e62f075ab119cbc565ea6
+  file: file1 (state "r")
     local path: file1 (flags "")
     ancestor path: file1 (node b8e02f6433738021a065f94175c7cd23db5f05be)
-    other path: file1 (node null)
-  file extras: file2 (ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff)
-  file: file2 (record type "C", state "u", hash null)
+    other path: file1 (node 0000000000000000000000000000000000000000)
+    extra: ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff
+  file: file2 (state "u")
     local path: file2 (flags "")
     ancestor path: file2 (node 5d9299349fc01ddd25d0070d149b124d8f10411e)
     other path: file2 (node e7c1328648519852e723de86c0c0525acd779257)
-  file extras: file3 (ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff)
-  file: file3 (record type "F", state "u", hash d5b0a58bc47161b1b8a831084b366f757c4f0b11)
+    extra: ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff
+  file: file3 (state "u")
     local path: file3 (flags "")
     ancestor path: file3 (node 2661d26c649684b482d10f91960cc3db683c38b4)
     other path: file3 (node a2644c43e210356772c7772a8674544a62e06beb)
+    extra: ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff
   *** file1 does not exist
   --- file2 ---
   2
@@ -346,27 +330,23 @@
   R file2
   R file3
   --- debugmergestate ---
-  * version 2 records
-  local: 13910f48cf7bdb2a0ba6e24b4900e4fdd5739dd4
-  other: 10f9a0a634e82080907e62f075ab119cbc565ea6
-  labels:
-    local: working copy
-    other: merge rev
-  file extras: file1 (ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff)
-  file: file1 (record type "C", state "r", hash 60b27f004e454aca81b0480209cce5081ec52390)
+  local (working copy): 13910f48cf7bdb2a0ba6e24b4900e4fdd5739dd4
+  other (merge rev): 10f9a0a634e82080907e62f075ab119cbc565ea6
+  file: file1 (state "r")
     local path: file1 (flags "")
     ancestor path: file1 (node b8e02f6433738021a065f94175c7cd23db5f05be)
-    other path: file1 (node null)
-  file extras: file2 (ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff)
-  file: file2 (record type "C", state "r", hash null)
+    other path: file1 (node 0000000000000000000000000000000000000000)
+    extra: ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff
+  file: file2 (state "r")
     local path: file2 (flags "")
     ancestor path: file2 (node 5d9299349fc01ddd25d0070d149b124d8f10411e)
     other path: file2 (node e7c1328648519852e723de86c0c0525acd779257)
-  file extras: file3 (ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff)
-  file: file3 (record type "F", state "r", hash d5b0a58bc47161b1b8a831084b366f757c4f0b11)
+    extra: ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff
+  file: file3 (state "r")
     local path: file3 (flags "")
     ancestor path: file3 (node 2661d26c649684b482d10f91960cc3db683c38b4)
     other path: file3 (node a2644c43e210356772c7772a8674544a62e06beb)
+    extra: ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff
   --- file1 ---
   1
   changed
@@ -395,27 +375,23 @@
   R file2
   R file3
   --- debugmergestate ---
-  * version 2 records
-  local: 13910f48cf7bdb2a0ba6e24b4900e4fdd5739dd4
-  other: 10f9a0a634e82080907e62f075ab119cbc565ea6
-  labels:
-    local: working copy
-    other: merge rev
-  file extras: file1 (ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff)
-  file: file1 (record type "C", state "r", hash 60b27f004e454aca81b0480209cce5081ec52390)
+  local (working copy): 13910f48cf7bdb2a0ba6e24b4900e4fdd5739dd4
+  other (merge rev): 10f9a0a634e82080907e62f075ab119cbc565ea6
+  file: file1 (state "r")
     local path: file1 (flags "")
     ancestor path: file1 (node b8e02f6433738021a065f94175c7cd23db5f05be)
-    other path: file1 (node null)
-  file extras: file2 (ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff)
-  file: file2 (record type "C", state "r", hash null)
+    other path: file1 (node 0000000000000000000000000000000000000000)
+    extra: ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff
+  file: file2 (state "r")
     local path: file2 (flags "")
     ancestor path: file2 (node 5d9299349fc01ddd25d0070d149b124d8f10411e)
     other path: file2 (node e7c1328648519852e723de86c0c0525acd779257)
-  file extras: file3 (ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff)
-  file: file3 (record type "F", state "r", hash d5b0a58bc47161b1b8a831084b366f757c4f0b11)
+    extra: ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff
+  file: file3 (state "r")
     local path: file3 (flags "")
     ancestor path: file3 (node 2661d26c649684b482d10f91960cc3db683c38b4)
     other path: file3 (node a2644c43e210356772c7772a8674544a62e06beb)
+    extra: ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff
   *** file1 does not exist
   --- file2 ---
   2
@@ -445,27 +421,23 @@
   U file2
   U file3
   --- debugmergestate ---
-  * version 2 records
-  local: 13910f48cf7bdb2a0ba6e24b4900e4fdd5739dd4
-  other: 10f9a0a634e82080907e62f075ab119cbc565ea6
-  labels:
-    local: working copy
-    other: merge rev
-  file extras: file1 (ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff)
-  file: file1 (record type "C", state "u", hash 60b27f004e454aca81b0480209cce5081ec52390)
+  local (working copy): 13910f48cf7bdb2a0ba6e24b4900e4fdd5739dd4
+  other (merge rev): 10f9a0a634e82080907e62f075ab119cbc565ea6
+  file: file1 (state "u")
     local path: file1 (flags "")
     ancestor path: file1 (node b8e02f6433738021a065f94175c7cd23db5f05be)
-    other path: file1 (node null)
-  file extras: file2 (ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff)
-  file: file2 (record type "C", state "u", hash null)
+    other path: file1 (node 0000000000000000000000000000000000000000)
+    extra: ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff
+  file: file2 (state "u")
     local path: file2 (flags "")
     ancestor path: file2 (node 5d9299349fc01ddd25d0070d149b124d8f10411e)
     other path: file2 (node e7c1328648519852e723de86c0c0525acd779257)
-  file extras: file3 (ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff)
-  file: file3 (record type "F", state "u", hash d5b0a58bc47161b1b8a831084b366f757c4f0b11)
+    extra: ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff
+  file: file3 (state "u")
     local path: file3 (flags "")
     ancestor path: file3 (node 2661d26c649684b482d10f91960cc3db683c38b4)
     other path: file3 (node a2644c43e210356772c7772a8674544a62e06beb)
+    extra: ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff
   --- file1 ---
   1
   changed
@@ -506,27 +478,23 @@
   U file2
   U file3
   --- debugmergestate ---
-  * version 2 records
-  local: 13910f48cf7bdb2a0ba6e24b4900e4fdd5739dd4
-  other: 10f9a0a634e82080907e62f075ab119cbc565ea6
-  labels:
-    local: working copy
-    other: merge rev
-  file extras: file1 (ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff)
-  file: file1 (record type "C", state "u", hash 60b27f004e454aca81b0480209cce5081ec52390)
+  local (working copy): 13910f48cf7bdb2a0ba6e24b4900e4fdd5739dd4
+  other (merge rev): 10f9a0a634e82080907e62f075ab119cbc565ea6
+  file: file1 (state "u")
     local path: file1 (flags "")
     ancestor path: file1 (node b8e02f6433738021a065f94175c7cd23db5f05be)
-    other path: file1 (node null)
-  file extras: file2 (ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff)
-  file: file2 (record type "C", state "u", hash null)
+    other path: file1 (node 0000000000000000000000000000000000000000)
+    extra: ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff
+  file: file2 (state "u")
     local path: file2 (flags "")
     ancestor path: file2 (node 5d9299349fc01ddd25d0070d149b124d8f10411e)
     other path: file2 (node e7c1328648519852e723de86c0c0525acd779257)
-  file extras: file3 (ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff)
-  file: file3 (record type "F", state "u", hash d5b0a58bc47161b1b8a831084b366f757c4f0b11)
+    extra: ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff
+  file: file3 (state "u")
     local path: file3 (flags "")
     ancestor path: file3 (node 2661d26c649684b482d10f91960cc3db683c38b4)
     other path: file3 (node a2644c43e210356772c7772a8674544a62e06beb)
+    extra: ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff
   --- file1 ---
   1
   changed
@@ -569,27 +537,23 @@
   U file2
   U file3
   --- debugmergestate ---
-  * version 2 records
-  local: 13910f48cf7bdb2a0ba6e24b4900e4fdd5739dd4
-  other: 10f9a0a634e82080907e62f075ab119cbc565ea6
-  labels:
-    local: working copy
-    other: merge rev
-  file extras: file1 (ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff)
-  file: file1 (record type "C", state "u", hash 60b27f004e454aca81b0480209cce5081ec52390)
+  local (working copy): 13910f48cf7bdb2a0ba6e24b4900e4fdd5739dd4
+  other (merge rev): 10f9a0a634e82080907e62f075ab119cbc565ea6
+  file: file1 (state "u")
     local path: file1 (flags "")
     ancestor path: file1 (node b8e02f6433738021a065f94175c7cd23db5f05be)
-    other path: file1 (node null)
-  file extras: file2 (ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff)
-  file: file2 (record type "C", state "u", hash null)
+    other path: file1 (node 0000000000000000000000000000000000000000)
+    extra: ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff
+  file: file2 (state "u")
     local path: file2 (flags "")
     ancestor path: file2 (node 5d9299349fc01ddd25d0070d149b124d8f10411e)
     other path: file2 (node e7c1328648519852e723de86c0c0525acd779257)
-  file extras: file3 (ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff)
-  file: file3 (record type "F", state "u", hash d5b0a58bc47161b1b8a831084b366f757c4f0b11)
+    extra: ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff
+  file: file3 (state "u")
     local path: file3 (flags "")
     ancestor path: file3 (node 2661d26c649684b482d10f91960cc3db683c38b4)
     other path: file3 (node a2644c43e210356772c7772a8674544a62e06beb)
+    extra: ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff
   --- file1 ---
   1
   changed
@@ -629,27 +593,23 @@
   U file2
   U file3
   --- debugmergestate ---
-  * version 2 records
-  local: 13910f48cf7bdb2a0ba6e24b4900e4fdd5739dd4
-  other: 10f9a0a634e82080907e62f075ab119cbc565ea6
-  labels:
-    local: working copy
-    other: merge rev
-  file extras: file1 (ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff)
-  file: file1 (record type "C", state "u", hash 60b27f004e454aca81b0480209cce5081ec52390)
+  local (working copy): 13910f48cf7bdb2a0ba6e24b4900e4fdd5739dd4
+  other (merge rev): 10f9a0a634e82080907e62f075ab119cbc565ea6
+  file: file1 (state "u")
     local path: file1 (flags "")
     ancestor path: file1 (node b8e02f6433738021a065f94175c7cd23db5f05be)
-    other path: file1 (node null)
-  file extras: file2 (ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff)
-  file: file2 (record type "C", state "u", hash null)
+    other path: file1 (node 0000000000000000000000000000000000000000)
+    extra: ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff
+  file: file2 (state "u")
     local path: file2 (flags "")
     ancestor path: file2 (node 5d9299349fc01ddd25d0070d149b124d8f10411e)
     other path: file2 (node e7c1328648519852e723de86c0c0525acd779257)
-  file extras: file3 (ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff)
-  file: file3 (record type "F", state "u", hash d5b0a58bc47161b1b8a831084b366f757c4f0b11)
+    extra: ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff
+  file: file3 (state "u")
     local path: file3 (flags "")
     ancestor path: file3 (node 2661d26c649684b482d10f91960cc3db683c38b4)
     other path: file3 (node a2644c43e210356772c7772a8674544a62e06beb)
+    extra: ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff
   --- file1 ---
   1
   changed
@@ -802,22 +762,18 @@
   U file1
   U file2
   --- debugmergestate ---
-  * version 2 records
-  local: ab57bf49aa276a22d35a473592d4c34b5abc3eff
-  other: 10f9a0a634e82080907e62f075ab119cbc565ea6
-  labels:
-    local: working copy
-    other: destination
-  file extras: file1 (ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff)
-  file: file1 (record type "C", state "u", hash 60b27f004e454aca81b0480209cce5081ec52390)
+  local (working copy): ab57bf49aa276a22d35a473592d4c34b5abc3eff
+  other (destination): 10f9a0a634e82080907e62f075ab119cbc565ea6
+  file: file1 (state "u")
     local path: file1 (flags "")
     ancestor path: file1 (node b8e02f6433738021a065f94175c7cd23db5f05be)
-    other path: file1 (node null)
-  file extras: file2 (ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff)
-  file: file2 (record type "C", state "u", hash null)
+    other path: file1 (node 0000000000000000000000000000000000000000)
+    extra: ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff
+  file: file2 (state "u")
     local path: file2 (flags "")
     ancestor path: file2 (node 5d9299349fc01ddd25d0070d149b124d8f10411e)
     other path: file2 (node e7c1328648519852e723de86c0c0525acd779257)
+    extra: ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff
   --- file1 ---
   1
   changed
@@ -845,22 +801,18 @@
   R file1
   R file2
   --- debugmergestate ---
-  * version 2 records
-  local: ab57bf49aa276a22d35a473592d4c34b5abc3eff
-  other: 10f9a0a634e82080907e62f075ab119cbc565ea6
-  labels:
-    local: working copy
-    other: destination
-  file extras: file1 (ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff)
-  file: file1 (record type "C", state "r", hash 60b27f004e454aca81b0480209cce5081ec52390)
+  local (working copy): ab57bf49aa276a22d35a473592d4c34b5abc3eff
+  other (destination): 10f9a0a634e82080907e62f075ab119cbc565ea6
+  file: file1 (state "r")
     local path: file1 (flags "")
     ancestor path: file1 (node b8e02f6433738021a065f94175c7cd23db5f05be)
-    other path: file1 (node null)
-  file extras: file2 (ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff)
-  file: file2 (record type "C", state "r", hash null)
+    other path: file1 (node 0000000000000000000000000000000000000000)
+    extra: ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff
+  file: file2 (state "r")
     local path: file2 (flags "")
     ancestor path: file2 (node 5d9299349fc01ddd25d0070d149b124d8f10411e)
     other path: file2 (node e7c1328648519852e723de86c0c0525acd779257)
+    extra: ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff
   --- file1 ---
   1
   changed
@@ -886,22 +838,18 @@
   R file1
   R file2
   --- debugmergestate ---
-  * version 2 records
-  local: ab57bf49aa276a22d35a473592d4c34b5abc3eff
-  other: 10f9a0a634e82080907e62f075ab119cbc565ea6
-  labels:
-    local: working copy
-    other: destination
-  file extras: file1 (ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff)
-  file: file1 (record type "C", state "r", hash 60b27f004e454aca81b0480209cce5081ec52390)
+  local (working copy): ab57bf49aa276a22d35a473592d4c34b5abc3eff
+  other (destination): 10f9a0a634e82080907e62f075ab119cbc565ea6
+  file: file1 (state "r")
     local path: file1 (flags "")
     ancestor path: file1 (node b8e02f6433738021a065f94175c7cd23db5f05be)
-    other path: file1 (node null)
-  file extras: file2 (ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff)
-  file: file2 (record type "C", state "r", hash null)
+    other path: file1 (node 0000000000000000000000000000000000000000)
+    extra: ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff
+  file: file2 (state "r")
     local path: file2 (flags "")
     ancestor path: file2 (node 5d9299349fc01ddd25d0070d149b124d8f10411e)
     other path: file2 (node e7c1328648519852e723de86c0c0525acd779257)
+    extra: ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff
   *** file1 does not exist
   --- file2 ---
   2
@@ -929,22 +877,18 @@
   U file1
   U file2
   --- debugmergestate ---
-  * version 2 records
-  local: ab57bf49aa276a22d35a473592d4c34b5abc3eff
-  other: 10f9a0a634e82080907e62f075ab119cbc565ea6
-  labels:
-    local: working copy
-    other: destination
-  file extras: file1 (ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff)
-  file: file1 (record type "C", state "u", hash 60b27f004e454aca81b0480209cce5081ec52390)
+  local (working copy): ab57bf49aa276a22d35a473592d4c34b5abc3eff
+  other (destination): 10f9a0a634e82080907e62f075ab119cbc565ea6
+  file: file1 (state "u")
     local path: file1 (flags "")
     ancestor path: file1 (node b8e02f6433738021a065f94175c7cd23db5f05be)
-    other path: file1 (node null)
-  file extras: file2 (ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff)
-  file: file2 (record type "C", state "u", hash null)
+    other path: file1 (node 0000000000000000000000000000000000000000)
+    extra: ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff
+  file: file2 (state "u")
     local path: file2 (flags "")
     ancestor path: file2 (node 5d9299349fc01ddd25d0070d149b124d8f10411e)
     other path: file2 (node e7c1328648519852e723de86c0c0525acd779257)
+    extra: ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff
   --- file1 ---
   1
   changed
@@ -980,22 +924,18 @@
   U file1
   U file2
   --- debugmergestate ---
-  * version 2 records
-  local: ab57bf49aa276a22d35a473592d4c34b5abc3eff
-  other: 10f9a0a634e82080907e62f075ab119cbc565ea6
-  labels:
-    local: working copy
-    other: destination
-  file extras: file1 (ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff)
-  file: file1 (record type "C", state "u", hash 60b27f004e454aca81b0480209cce5081ec52390)
+  local (working copy): ab57bf49aa276a22d35a473592d4c34b5abc3eff
+  other (destination): 10f9a0a634e82080907e62f075ab119cbc565ea6
+  file: file1 (state "u")
     local path: file1 (flags "")
     ancestor path: file1 (node b8e02f6433738021a065f94175c7cd23db5f05be)
-    other path: file1 (node null)
-  file extras: file2 (ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff)
-  file: file2 (record type "C", state "u", hash null)
+    other path: file1 (node 0000000000000000000000000000000000000000)
+    extra: ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff
+  file: file2 (state "u")
     local path: file2 (flags "")
     ancestor path: file2 (node 5d9299349fc01ddd25d0070d149b124d8f10411e)
     other path: file2 (node e7c1328648519852e723de86c0c0525acd779257)
+    extra: ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff
   --- file1 ---
   1
   changed
@@ -1032,22 +972,18 @@
   U file1
   U file2
   --- debugmergestate ---
-  * version 2 records
-  local: ab57bf49aa276a22d35a473592d4c34b5abc3eff
-  other: 10f9a0a634e82080907e62f075ab119cbc565ea6
-  labels:
-    local: working copy
-    other: destination
-  file extras: file1 (ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff)
-  file: file1 (record type "C", state "u", hash 60b27f004e454aca81b0480209cce5081ec52390)
+  local (working copy): ab57bf49aa276a22d35a473592d4c34b5abc3eff
+  other (destination): 10f9a0a634e82080907e62f075ab119cbc565ea6
+  file: file1 (state "u")
     local path: file1 (flags "")
     ancestor path: file1 (node b8e02f6433738021a065f94175c7cd23db5f05be)
-    other path: file1 (node null)
-  file extras: file2 (ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff)
-  file: file2 (record type "C", state "u", hash null)
+    other path: file1 (node 0000000000000000000000000000000000000000)
+    extra: ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff
+  file: file2 (state "u")
     local path: file2 (flags "")
     ancestor path: file2 (node 5d9299349fc01ddd25d0070d149b124d8f10411e)
     other path: file2 (node e7c1328648519852e723de86c0c0525acd779257)
+    extra: ancestorlinknode = ab57bf49aa276a22d35a473592d4c34b5abc3eff
   --- file1 ---
   1
   changed
diff --git a/tests/test-rebase-abort.t b/tests/test-rebase-abort.t
--- a/tests/test-rebase-abort.t
+++ b/tests/test-rebase-abort.t
@@ -88,18 +88,13 @@
 
   $ hg --config extensions.fakemergerecord=$TESTDIR/fakemergerecord.py fakemergerecord -x
   $ hg debugmergestate
-  * version 2 records
-  local: 3e046f2ecedb793b97ed32108086edd1a162f8bc
-  other: 46f0b057b5c061d276b91491c22151f78698abd2
-  labels:
-    local: dest
-    other: source
-  unrecognized entry: x	advisory record
-  file extras: common (ancestorlinknode = 3163e20567cc93074fbb7a53c8b93312e59dbf2c)
-  file: common (record type "F", state "u", hash 94c8c21d08740f5da9eaa38d1f175c592692f0d1)
+  local (dest): 3e046f2ecedb793b97ed32108086edd1a162f8bc
+  other (source): 46f0b057b5c061d276b91491c22151f78698abd2
+  file: common (state "u")
     local path: common (flags "")
     ancestor path: common (node de0a666fdd9c1a0b0698b90d85064d8bd34f74b6)
     other path: common (node 2f6411de53677f6f1048fef5bf888d67a342e0a5)
+    extra: ancestorlinknode = 3163e20567cc93074fbb7a53c8b93312e59dbf2c
   $ hg resolve -l
   U common
 
@@ -107,18 +102,9 @@
 
   $ hg --config extensions.fakemergerecord=$TESTDIR/fakemergerecord.py fakemergerecord -X
   $ hg debugmergestate
-  * version 2 records
-  local: 3e046f2ecedb793b97ed32108086edd1a162f8bc
-  other: 46f0b057b5c061d276b91491c22151f78698abd2
-  labels:
-    local: dest
-    other: source
-  file extras: common (ancestorlinknode = 3163e20567cc93074fbb7a53c8b93312e59dbf2c)
-  file: common (record type "F", state "u", hash 94c8c21d08740f5da9eaa38d1f175c592692f0d1)
-    local path: common (flags "")
-    ancestor path: common (node de0a666fdd9c1a0b0698b90d85064d8bd34f74b6)
-    other path: common (node 2f6411de53677f6f1048fef5bf888d67a342e0a5)
-  unrecognized entry: X	mandatory record
+  abort: unsupported merge state records: X
+  (see https://mercurial-scm.org/wiki/MergeStateRecords for more information)
+  [255]
   $ hg resolve -l
   abort: unsupported merge state records: X
   (see https://mercurial-scm.org/wiki/MergeStateRecords for more information)
diff --git a/tests/test-resolve.t b/tests/test-resolve.t
--- a/tests/test-resolve.t
+++ b/tests/test-resolve.t
@@ -306,48 +306,40 @@
 
   $ hg --config extensions.fakemergerecord=$TESTDIR/fakemergerecord.py fakemergerecord -x
   $ hg debugmergestate
-  * version 2 records
-  local: 57653b9f834a4493f7240b0681efcb9ae7cab745
-  other: dc77451844e37f03f5c559e3b8529b2b48d381d1
-  labels:
-    local: working copy
-    other: merge rev
-  unrecognized entry: x	advisory record
-  file extras: file1 (ancestorlinknode = 99726c03216e233810a2564cbc0adfe395007eac)
-  file: file1 (record type "F", state "r", hash 60b27f004e454aca81b0480209cce5081ec52390)
+  local (working copy): 57653b9f834a4493f7240b0681efcb9ae7cab745
+  other (merge rev): dc77451844e37f03f5c559e3b8529b2b48d381d1
+  file: file1 (state "r")
     local path: file1 (flags "")
     ancestor path: file1 (node 2ed2a3912a0b24502043eae84ee4b279c18b90dd)
     other path: file1 (node 6f4310b00b9a147241b071a60c28a650827fb03d)
-  file extras: file2 (ancestorlinknode = 99726c03216e233810a2564cbc0adfe395007eac)
-  file: file2 (record type "F", state "u", hash cb99b709a1978bd205ab9dfd4c5aaa1fc91c7523)
+    extra: ancestorlinknode = 99726c03216e233810a2564cbc0adfe395007eac
+  file: file2 (state "u")
     local path: file2 (flags "")
     ancestor path: file2 (node 2ed2a3912a0b24502043eae84ee4b279c18b90dd)
     other path: file2 (node 6f4310b00b9a147241b071a60c28a650827fb03d)
+    extra: ancestorlinknode = 99726c03216e233810a2564cbc0adfe395007eac
   $ hg resolve -l
   R file1
   U file2
 
+test json output
+
+  $ hg debugmergestate -T json
+  [
+   {
+    "commits": [{"label": "working copy", "name": "local", "node": "57653b9f834a4493f7240b0681efcb9ae7cab745"}, {"label": "merge rev", "name": "other", "node": "dc77451844e37f03f5c559e3b8529b2b48d381d1"}],
+    "files": [{"ancestor_node": "2ed2a3912a0b24502043eae84ee4b279c18b90dd", "ancestor_path": "file1", "extras": [{"key": "ancestorlinknode", "value": "99726c03216e233810a2564cbc0adfe395007eac"}], "local_flags": "", "local_key": "60b27f004e454aca81b0480209cce5081ec52390", "local_path": "file1", "other_node": "6f4310b00b9a147241b071a60c28a650827fb03d", "other_path": "file1", "path": "file1", "state": "r"}, {"ancestor_node": "2ed2a3912a0b24502043eae84ee4b279c18b90dd", "ancestor_path": "file2", "extras": [{"key": "ancestorlinknode", "value": "99726c03216e233810a2564cbc0adfe395007eac"}], "local_flags": "", "local_key": "cb99b709a1978bd205ab9dfd4c5aaa1fc91c7523", "local_path": "file2", "other_node": "6f4310b00b9a147241b071a60c28a650827fb03d", "other_path": "file2", "path": "file2", "state": "u"}]
+   }
+  ]
+
+
 insert unsupported mandatory merge record
 
   $ hg --config extensions.fakemergerecord=$TESTDIR/fakemergerecord.py fakemergerecord -X
   $ hg debugmergestate
-  * version 2 records
-  local: 57653b9f834a4493f7240b0681efcb9ae7cab745
-  other: dc77451844e37f03f5c559e3b8529b2b48d381d1
-  labels:
-    local: working copy
-    other: merge rev
-  file extras: file1 (ancestorlinknode = 99726c03216e233810a2564cbc0adfe395007eac)
-  file: file1 (record type "F", state "r", hash 60b27f004e454aca81b0480209cce5081ec52390)
-    local path: file1 (flags "")
-    ancestor path: file1 (node 2ed2a3912a0b24502043eae84ee4b279c18b90dd)
-    other path: file1 (node 6f4310b00b9a147241b071a60c28a650827fb03d)
-  file extras: file2 (ancestorlinknode = 99726c03216e233810a2564cbc0adfe395007eac)
-  file: file2 (record type "F", state "u", hash cb99b709a1978bd205ab9dfd4c5aaa1fc91c7523)
-    local path: file2 (flags "")
-    ancestor path: file2 (node 2ed2a3912a0b24502043eae84ee4b279c18b90dd)
-    other path: file2 (node 6f4310b00b9a147241b071a60c28a650827fb03d)
-  unrecognized entry: X	mandatory record
+  abort: unsupported merge state records: X
+  (see https://mercurial-scm.org/wiki/MergeStateRecords for more information)
+  [255]
   $ hg resolve -l
   abort: unsupported merge state records: X
   (see https://mercurial-scm.org/wiki/MergeStateRecords for more information)