diff --git a/contrib/relnotes b/contrib/relnotes
new file mode 100644
--- /dev/null
+++ b/contrib/relnotes
@@ -0,0 +1,179 @@
+#!/usr/bin/env python3
+"""Generate release notes from our commit log.
+
+This uses the relnotes extension directives when they're available,
+and falls back to our old pre-relnotes logic that used to live in the
+release-tools repo.
+"""
+import argparse
+import re
+import subprocess
+
+# Regenerate this list with
+#   hg export 'grep("\.\. [a-z]+::")' | grep '^\.\.' | \
+#     sed 's/.. //;s/::.*//' | sort -u
+rnsections = ["api", "bc", "container", "feature", "fix", "note", "perf"]
+
+rules = {
+    # keep
+    r"\(issue": 100,
+    r"\(BC\)": 100,
+    r"\(API\)": 100,
+    # core commands, bump up
+    r"(commit|files|log|pull|push|patch|status|tag|summary)(|s|es):": 20,
+    r"(annotate|alias|branch|bookmark|clone|graft|import|verify).*:": 20,
+    # extensions, bump up
+    r"(mq|shelve|rebase):": 20,
+    # newsy
+    r": deprecate": 20,
+    r"(option|feature|command|support)": 10,
+    # bug-like?
+    r"(fix|don't break|improve)": 7,
+    # boring stuff, bump down
+    r"^contrib": -5,
+    r"debug": -5,
+    r"help": -5,
+    r"(doc|bundle2|obsolete|obsmarker|rpm|setup|debug\S+:)": -15,
+    r"(check-code|check-commit|import-checker)": -20,
+    # cleanups and refactoring
+    r"(cleanup|whitespace|nesting|indent|spelling|comment)": -20,
+    r"(typo|hint|note|style:|correct doc)": -20,
+    r"_": -10,
+    r"(argument|absolute_import|attribute|assignment|mutable)": -15,
+    r"(unused|useless|unnecessary|duplicate|deprecated|scope|True|False)": -10,
+    r"(redundant|pointless|confusing|uninitialized|meaningless|dead)": -10,
+    r": (drop|remove|inherit|rename|simplify|naming|inline)": -10,
+    r"(docstring|document .* method)": -20,
+    r"(factor|extract|prepare|split|replace| import)": -20,
+    r": add.*(function|method|implementation|test|example)": -10,
+    r": (move|extract) .* (to|into|from)": -20,
+    r": implement ": -5,
+    r": use .* implementation": -20,
+    r"\S\S\S+\.\S\S\S\S+": -5,
+    r": use .* instead of": -20,
+    r"__": -5,
+    # dumb keywords
+    r"\S+/\S+:": -10,
+    r"\S+\.\S+:": -10,
+    # drop
+    r"^i18n-": -50,
+    r"^i18n:.*(hint|comment)": -50,
+    r"perf:": -50,
+    r"check-code:": -50,
+    r"Added.*for changeset": -50,
+    r"tests?:": -50,
+    r"test-": -50,
+    r"add.* tests": -50,
+    r"^_": -50,
+}
+
+cutoff = 10
+commits = []
+
+groupings = [
+    (r"util|parsers|repo|ctx|context|revlog|filelog|alias|cmdutil", "core"),
+    (r"revset|templater|ui|dirstate|hook|i18n|transaction|wire", "core"),
+    (r"color|pager", "core"),
+    (r"hgweb|paper|coal|gitweb", "hgweb"),
+    (r"pull|push|revert|resolve|annotate|bookmark|branch|clone", "commands"),
+    (r"commands|commit|config|files|graft|import|log|merge|patch", "commands"),
+    (r"phases|status|summary|amend|tag|help|verify", "commands"),
+    (r"rebase|mq|convert|eol|histedit|largefiles", "extensions"),
+    (r"shelve|unshelve", "extensions"),
+]
+
+def main():
+    ap = argparse.ArgumentParser()
+    ap.add_argument(
+        "startrev",
+        metavar="REV",
+        type=str,
+        nargs=1,
+        help=(
+            "Starting revision for the release notes. This revision "
+            "won't be included, but later revisions will."
+        ),
+    )
+    ap.add_argument(
+        "--stoprev",
+        metavar="REV",
+        type=str,
+        default="@",
+        nargs=1,
+        help=(
+            "Stop revision for release notes. This revision will be included,"
+            " but no later revisions will. This revision needs to be "
+            "a descendant of startrev."
+        ),
+    )
+    args = ap.parse_args()
+    fromext = subprocess.check_output(
+        [
+            "hg",
+            "releasenotes",
+            "-r",
+            "%s::%s" % (args.startrev[0], args.stoprev[0]),
+        ]
+    ).decode("utf-8")
+    # Find all release notes from un-relnotes-flagged commits.
+    for entry in sorted(
+        subprocess.check_output(
+            [
+                "hg",
+                "log",
+                "-r",
+                r'%s::%s - merge() - grep("\n\.\. (%s)::")'
+                % (args.startrev[0], args.stoprev[0], "|".join(rnsections)),
+                "-T",
+                r"{desc|firstline}\n",
+            ]
+        )
+        .decode("utf-8")
+        .splitlines()
+    ):
+        desc = entry.replace("`", "'")
+
+        score = 0
+        for rule, val in rules.items():
+            if re.search(rule, desc):
+                score += val
+
+        desc = desc.replace("(issue", "(Bts:issue")
+
+        if score >= cutoff:
+            commits.append(desc)
+    # Group unflagged notes.
+    groups = {}
+    bcs = []
+    apis = []
+
+    for d in commits:
+        if "(BC)" in d:
+            bcs.append(d)
+        if "(API)" in d:
+            apis.append(d)
+        for rule, g in groupings:
+            if re.match(rule, d):
+                groups.setdefault(g, []).append(d)
+                break
+        else:
+            groups.setdefault("unsorted", []).append(d)
+    print(fromext)
+    # print legacy release notes sections
+    for g in sorted(groups):
+        print("\n=== %s ===" % g)
+        for d in sorted(groups[g]):
+            print(" * %s" % d)
+
+    print("\n=== BC ===\n")
+
+    for d in sorted(bcs):
+        print(" * %s" % d)
+
+    print("\n=== API Changes ===\n")
+
+    for d in sorted(apis):
+        print(" * %s" % d)
+
+if __name__ == "__main__":
+    main()
diff --git a/tests/test-contrib-relnotes.t b/tests/test-contrib-relnotes.t
new file mode 100644
--- /dev/null
+++ b/tests/test-contrib-relnotes.t
@@ -0,0 +1,290 @@
+#require test-repo py3exe
+  $ . "$TESTDIR/helpers-testrepo.sh"
+
+  $ cd $TESTDIR/..
+  $ python3 contrib/relnotes 4.4 --stoprev 4.5
+  New Features
+  ============
+  
+  revert --interactive
+  --------------------
+  
+  The revert command now accepts the flag --interactive to allow reverting only
+  some of the changes to the specified files.
+  
+  Rebase with different destination per source revision
+  -----------------------------------------------------
+  
+  Previously, rebase only supports one unique destination. Now "SRC" and
+  "ALLSRC" can be used in rebase destination revset to precisely define
+  destination per each individual source revision.
+  
+  For example, the following command could move some orphaned changesets to
+  reasonable new places so they become no longer orphaned:
+  
+  hg rebase   -r 'orphan()-obsolete()'   -d 'max((successors(max(roots(ALLSRC) &
+  ::SRC)^)-obsolete())::)'
+  
+  Accessing hidden changesets
+  ---------------------------
+  
+  Set config option 'experimental.directaccess = True' to access hidden
+  changesets from read only commands.
+  
+  githelp extension
+  -----------------
+  
+  The "githelp" extension provides the "hg githelp" command. This command
+  attempts to convert a "git" command to its Mercurial equivalent. The extension
+  can be useful to Git users new to Mercurial.
+  
+  Other Changes
+  -------------
+  
+  * When interactive revert is run against a revision other than the working
+    directory parent, the diff shown is the diff to *apply* to the working
+    directory, rather than the diff to *discard* from the working copy. This is
+    in line with related user experiences with 'git' and appears to be less
+    confusing with 'ui.interface=curses'.
+  
+  * Let 'hg rebase' avoid content-divergence by skipping obsolete changesets
+    (and their descendants) when they are present in the rebase set along with
+    one of their successors but none of their successors is in destination.
+  
+  * hgweb now displays phases of non-public changesets
+  
+  * The "HGPLAINEXCEPT" environment variable can now include "color" to allow
+    automatic output colorization in otherwise automated environments.
+  
+  * A new unamend command in uncommit extension which undoes the effect of the
+    amend command by creating a new changeset which was there before amend and
+    moving the changes that were amended to the working directory.
+  
+  * A '--abort' flag to merge command to abort the ongoing merge.
+  
+  * An experimental flag '--rev' to 'hg branch' which can be used to change
+    branch of changesets.
+  
+  Backwards Compatibility Changes
+  ===============================
+  
+  * "log --follow-first -rREV", which is deprecated, now follows the first
+    parent of merge revisions from the specified "REV" just like "log --follow
+    -rREV".
+  
+  * "log --follow -rREV FILE.." now follows file history across copies and
+    renames.
+  
+  Bug Fixes
+  =========
+  
+  Issue 5165
+  ----------
+  
+  Bookmark, whose name is longer than 255, can again be exchanged again between
+  4.4+ client and servers.
+  
+  Performance Improvements
+  ========================
+  
+  * bundle2 read I/O throughput significantly increased.
+  
+  * Significant memory use reductions when reading from bundle2 bundles.
+  
+    On the BSD repository, peak RSS during changegroup application decreased by
+    ~185 MB from ~752 MB to ~567 MB.
+  
+  API Changes
+  ===========
+  
+  * bundlerepo.bundlerepository.bundle and
+    bundlerepo.bundlerepository.bundlefile are now prefixed with an underscore.
+  
+  * Rename bundlerepo.bundlerepository.bundlefilespos to _cgfilespos.
+  
+  * dirstate no longer provides a 'dirs()' method.  To test for the existence of
+    a directory in the dirstate, use 'dirstate.hasdir(dirname)'.
+  
+  * bundle2 parts are no longer seekable by default.
+  
+  * mapping does not contain all template resources. use context.resource() in
+    template functions.
+  
+  * "text=False|True" option is dropped from the vfs interface because of Python
+    3 compatibility issue. Use "util.tonativeeol/fromnativeeol()" to convert EOL
+    manually.
+  
+  * wireproto.streamres.__init__ no longer accepts a "reader" argument. Use the
+    "gen" argument instead.
+  
+  * exchange.getbundlechunks() now returns a 2-tuple instead of just an
+    iterator.
+  
+  
+  === commands ===
+   * amend: do not drop missing files (Bts:issue5732)
+   * amend: do not take untracked files as modified or clean (Bts:issue5732)
+   * amend: update .hgsubstate before committing a memctx (Bts:issue5677)
+   * annotate: add support to specify hidden revs if directaccess config is set
+   * bookmark: add methods to binary encode and decode bookmark values
+   * bookmark: deprecate direct update of a bookmark value
+   * bookmark: introduce a 'bookmarks' part
+   * bookmark: introduce in advance a variant of the exchange test
+   * bookmark: run 'pushkey' hooks after bookmark move, not 'prepushkey'
+   * bookmarks: add bookmarks to hidden revs if directaccess config is set
+   * bookmarks: calculate visibility exceptions only once
+   * bookmarks: display the obsfate of hidden revision we create a bookmark on
+   * bookmarks: fix pushkey compatibility mode (Bts:issue5777)
+   * bookmarks: use context managers for lock and transaction in update()
+   * bookmarks: use context managers for locks and transaction in pushbookmark()
+   * branch: allow changing branch name to existing name if possible
+   * clone: add support for storing remotenames while cloning
+   * clone: use utility function to write hgrc
+   * clonebundle: make it possible to retrieve the initial bundle through largefile
+   * commandserver: restore cwd in case of exception
+   * commandserver: unblock SIGCHLD
+   * help: deprecate ui.slash in favor of slashpath template filter (Bts:issue5572)
+   * log: allow matchfn to be non-null even if both --patch/--stat are off
+   * log: build follow-log filematcher at once
+   * log: don't expand aliases in revset built from command options
+   * log: make "slowpath" condition slightly more readable
+   * log: make opt2revset table a module constant
+   * log: merge getlogrevs() and getgraphlogrevs()
+   * log: remove temporary variable 'date' used only once
+   * log: resolve --follow thoroughly in getlogrevs()
+   * log: resolve --follow with -rREV in cmdutil.getlogrevs()
+   * log: simplify 'x or ancestors(x)' expression
+   * log: translate column labels at once (Bts:issue5750)
+   * log: use revsetlang.formatspec() thoroughly
+   * log: use revsetlang.formatspec() to concatenate list expression
+   * log: use smartset.slice() to limit number of revisions to be displayed
+   * merge: cache unknown dir checks (Bts:issue5716)
+   * merge: check created file dirs for path conflicts only once (Bts:issue5716)
+   * patch: add within-line color diff capacity
+   * patch: catch unexpected case in _inlinediff
+   * patch: do not break up multibyte character when highlighting word
+   * patch: improve heuristics to not take the word "diff" as header (Bts:issue1879)
+   * patch: reverse _inlinediff output for consistency
+   * pull: clarify that -u only updates linearly
+   * pull: hold wlock for the full operation when --update is used
+   * pull: retrieve bookmarks through the binary part when possible
+   * pull: store binary node in pullop.remotebookmarks
+   * push: include a 'check:bookmarks' part when possible
+   * push: restrict common discovery to the pushed set
+   * revert: support reverting to hidden cset if directaccess config is set
+  
+  === core ===
+   * filelog: add the ability to report the user facing name
+   * revlog: choose between ifh and dfh once for all
+   * revlog: don't use slicing to return parents
+   * revlog: group delta computation methods under _deltacomputer object
+   * revlog: group revision info into a dedicated structure
+   * revlog: introduce 'deltainfo' to distinguish from 'delta'
+   * revlog: rename 'rev' to 'base', as it is the base revision
+   * revlog: separate diff computation from the collection of other info
+   * revset: evaluate filesets against each revision for 'file()' (Bts:issue5778)
+   * revset: parse x^:: as (x^):: (Bts:issue5764)
+   * templater: look up symbols/resources as if they were separated (Bts:issue5699)
+   * transaction: register summary callbacks only at start of transaction (BC)
+   * util: whitelist NTFS for hardlink creation (Bts:issue4580)
+  
+  === extensions ===
+   * convert: restore the ability to use bzr < 2.6.0 (Bts:issue5733)
+   * histedit: add support to output nodechanges using formatter
+   * largefiles: add a 'debuglfput' command to put largefile into the store
+   * largefiles: add support for 'largefiles://' url scheme
+   * largefiles: allow to run 'debugupgraderepo' on repo with largefiles
+   * largefiles: convert EOL of hgrc before appending to bytes IO
+   * largefiles: explicitly set the source and sink types to 'hg' for lfconvert
+   * largefiles: modernize how capabilities are added to the wire protocol
+   * largefiles: pay attention to dropped standin files when updating largefiles
+   * rebase: add concludememorynode(), and call it when rebasing in-memory
+   * rebase: add the --inmemory option flag; assign a wctx object for the rebase
+   * rebase: add ui.log calls for whether IMM used, whether rebasing WCP
+   * rebase: disable 'inmemory' if the rebaseset contains the working copy
+   * rebase: do not bail on uncomitted changes if rebasing in-memory
+   * rebase: do not update if IMM; instead, set the overlaywctx's parents
+   * rebase: don't run IMM if running rebase in a transaction
+   * rebase: don't take out a dirstate guard for in-memory rebase
+   * rebase: drop --style option
+   * rebase: fix for hgsubversion
+   * rebase: pass the wctx object (IMM or on-disk) to merge.update
+   * rebase: pass wctx to rebasenode()
+   * rebase: rerun a rebase on-disk if IMM merge conflicts arise
+   * rebase: switch ui.log calls to common style
+   * rebase: use fm.formatlist() and fm.formatdict() to support user template
+  
+  === hgweb ===
+   * hgweb: disable diff.noprefix option for diffstat
+   * hgweb: drop support of browsers that don't understand <canvas> (BC)
+   * hgweb: only include graph-related data in jsdata variable on /graph pages (BC)
+   * hgweb: stop adding strings to innerHTML of #graphnodes and #nodebgs (BC)
+  
+  === unsorted ===
+   * archive: add support to specify hidden revs if directaccess config is set
+   * atomicupdate: add an experimental option to use atomictemp when updating
+   * bundle: allow bundlerepo to support alternative manifest implementations
+   * changelog: introduce a 'tiprev' method
+   * changelog: use 'tiprev()' in 'tip()'
+   * completion: add support for new "amend" command
+   * debugssl: convert port number to int (Bts:issue5757)
+   * diff: disable diff.noprefix option for diffstat (Bts:issue5759)
+   * dispatch: abort if early boolean options can't be parsed
+   * dispatch: add HGPLAIN=+strictflags to restrict early parsing of global options
+   * dispatch: add option to not strip command args parsed by _earlygetopt()
+   * dispatch: alias --repo to --repository while parsing early options
+   * dispatch: convert non-list option parsed by _earlygetopt() to string
+   * dispatch: fix early parsing of short option with value like -R=foo
+   * dispatch: handle IOError when writing to stderr
+   * dispatch: stop parsing of early boolean option at "--"
+   * dispatch: verify result of early command parsing
+   * evolution: make reporting of new unstable changesets optional
+   * extdata: abort if external command exits with non-zero status (BC)
+   * fancyopts: add early-options parser compatible with getopt()
+   * graphlog: add another graph node type, unstable, using character "*" (BC)
+   * hgdemandimport: use correct hyperlink to python-bug in comments (Bts:issue5765)
+   * httppeer: add support for tracing all http request made by the peer
+   * identify: document -r. explicitly how to disable wdir scanning (Bts:issue5622)
+   * lfs: register config options
+   * localrepo: specify optional callback parameter to pathauditor as a keyword
+   * match: do not weirdly include explicit files excluded by -X option
+   * memfilectx: make changectx argument mandatory in constructor (API)
+   * morestatus: don't crash with different drive letters for repo.root and CWD
+   * outgoing: respect ":pushurl" paths (Bts:issue5365)
+   * remove: print message for each file in verbose mode only while using '-A' (BC)
+   * rewriteutil: use precheck() in uncommit and amend commands
+   * scmutil: don't try to delete origbackup symlinks to directories (Bts:issue5731)
+   * sshpeer: add support for request tracing
+   * streamclone: add support for bundle2 based stream clone
+   * streamclone: add support for cloning non append-only file
+   * streamclone: also stream caches to the client
+   * streamclone: define first iteration of version 2 of stream format
+   * streamclone: move wire protocol status code from wireproto command
+   * streamclone: rework canperformstreamclone
+   * streamclone: tests phase exchange during stream clone
+   * streamclone: use readexactly when reading stream v2
+   * subrepo: add config option to reject any subrepo operations (SEC)
+   * subrepo: disable git and svn subrepos by default (BC) (SEC)
+   * subrepo: extend config option to disable subrepos by type (SEC)
+   * subrepo: handle 'C:' style paths on the command line (Bts:issue5770)
+   * subrepo: use per-type config options to enable subrepos
+   * svnsubrepo: check if subrepo is missing when checking dirty state (Bts:issue5657)
+   * tr-summary: keep a weakref to the unfiltered repository
+   * unamend: fix command summary line
+   * uncommit: unify functions _uncommitdirstate and _unamenddirstate to one
+   * update: support updating to hidden cset if directaccess config is set
+  
+  === BC ===
+  
+   * extdata: abort if external command exits with non-zero status (BC)
+   * graphlog: add another graph node type, unstable, using character "*" (BC)
+   * hgweb: drop support of browsers that don't understand <canvas> (BC)
+   * hgweb: only include graph-related data in jsdata variable on /graph pages (BC)
+   * hgweb: stop adding strings to innerHTML of #graphnodes and #nodebgs (BC)
+   * remove: print message for each file in verbose mode only while using '-A' (BC)
+   * subrepo: disable git and svn subrepos by default (BC) (SEC)
+   * transaction: register summary callbacks only at start of transaction (BC)
+  
+  === API Changes ===
+  
+   * memfilectx: make changectx argument mandatory in constructor (API)