diff --git a/hgext/fix.py b/hgext/fix.py
--- a/hgext/fix.py
+++ b/hgext/fix.py
@@ -214,6 +214,13 @@
     _(b'REV'),
 )
 revopt = (b'r', b'rev', [], _(b'revisions to fix'), _(b'REV'))
+sourceopt = (
+    b's',
+    b'source',
+    [],
+    _(b'fix the specified revisions and their descendants'),
+    _(b'REV'),
+)
 wdiropt = (b'w', b'working-dir', False, _(b'fix the working directory'))
 wholeopt = (b'', b'whole', False, _(b'always fix every line of a file'))
 usage = _(b'[OPTION]... [FILE]...')
@@ -221,7 +228,7 @@
 
 @command(
     b'fix',
-    [allopt, baseopt, revopt, wdiropt, wholeopt],
+    [allopt, baseopt, revopt, sourceopt, wdiropt, wholeopt],
     usage,
     helpcategory=command.CATEGORY_FILE_CONTENTS,
 )
@@ -249,7 +256,7 @@
     override this default behavior, though it is not usually desirable to do so.
     """
     opts = pycompat.byteskwargs(opts)
-    cmdutil.check_at_most_one_arg(opts, b'all', b'rev')
+    cmdutil.check_at_most_one_arg(opts, b'all', b'source', b'rev')
 
     with repo.wlock(), repo.lock(), repo.transaction(b'fix'):
         revstofix = getrevstofix(ui, repo, opts)
@@ -398,6 +405,14 @@
     """Returns the set of revision numbers that should be fixed"""
     if opts[b'all']:
         revs = repo.revs(b'(not public() and not obsolete()) or wdir()')
+    elif opts[b'source']:
+        source_revs = scmutil.revrange(repo, opts[b'source'])
+        revs = set(repo.revs(b'%ld::', source_revs))
+        if wdirrev in source_revs:
+            # `wdir()::` is currently empty, so manually add wdir
+            revs.add(wdirrev)
+        if repo[b'.'].rev() in revs:
+            revs.add(wdirrev)
     else:
         revs = set(scmutil.revrange(repo, opts[b'rev']))
         if opts.get(b'working_dir'):
diff --git a/tests/test-fix-topology.t b/tests/test-fix-topology.t
--- a/tests/test-fix-topology.t
+++ b/tests/test-fix-topology.t
@@ -21,6 +21,7 @@
   $ cat >> $HGRCPATH <<EOF
   > [extensions]
   > fix =
+  > strip =
   > [fix]
   > uppercase-whole-file:command="$PYTHON" $UPPERCASEPY
   > uppercase-whole-file:pattern=set:**
@@ -262,6 +263,111 @@
 
   $ cd ..
 
+
+Test the --source option. We only do this with obsstore on to avoid duplicating
+test code. We rely on the other tests to prove that obsolescence is not an
+important factor here.
+
+#if obsstore-on
+  $ hg init source-arg
+  $ cd source-arg
+  $ printf "aaaa\n" > a
+  $ hg commit -Am "change A"
+  adding a
+  $ printf "bbbb\n" > b
+  $ hg commit -Am "change B"
+  adding b
+  $ printf "cccc\n" > c
+  $ hg commit -Am "change C"
+  adding c
+  $ hg checkout 0
+  0 files updated, 0 files merged, 2 files removed, 0 files unresolved
+  $ printf "dddd\n" > d
+  $ hg commit -Am "change D"
+  adding d
+  created new head
+  $ hg log --graph --template '{rev} {desc}\n'
+  @  3 change D
+  |
+  | o  2 change C
+  | |
+  | o  1 change B
+  |/
+  o  0 change A
+  
+
+Test passing 'wdir()' to --source
+  $ printf "xxxx\n" > x
+  $ hg add x
+  $ hg fix -s 'wdir()'
+  $ cat *
+  aaaa
+  dddd
+  XXXX
+
+Test passing '.' to --source
+  $ printf "xxxx\n" > x
+  $ hg fix -s .
+  $ hg log --graph --template '{rev} {desc}\n'
+  @  4 change D
+  |
+  | o  2 change C
+  | |
+  | o  1 change B
+  |/
+  o  0 change A
+  
+  $ cat *
+  aaaa
+  DDDD
+  XXXX
+  $ hg strip -qf 4
+  $ hg co -q 3
+
+Test passing other branch to --source
+  $ printf "xxxx\n" > x
+  $ hg add x
+  $ hg fix -s 2
+  $ hg log --graph --template '{rev} {desc}\n'
+  o  4 change C
+  |
+  | @  3 change D
+  | |
+  o |  1 change B
+  |/
+  o  0 change A
+  
+  $ hg cat -r 4 b c
+  bbbb
+  CCCC
+  $ cat *
+  aaaa
+  dddd
+  xxxx
+  $ hg strip -qf 4
+
+Test passing multiple revisions to --source
+  $ hg fix -s '2 + .'
+  $ hg log --graph --template '{rev} {desc}\n'
+  @  5 change D
+  |
+  | o  4 change C
+  | |
+  | o  1 change B
+  |/
+  o  0 change A
+  
+  $ hg cat -r 4 b c
+  bbbb
+  CCCC
+  $ cat *
+  aaaa
+  DDDD
+  XXXX
+
+  $ cd ..
+#endif
+
 The --all flag should fix anything that wouldn't cause a problem if you fixed
 it, including the working copy. Obsolete revisions are not fixed because that
 could cause divergence. Public revisions would cause an abort because they are
diff --git a/tests/test-fix.t b/tests/test-fix.t
--- a/tests/test-fix.t
+++ b/tests/test-fix.t
@@ -104,12 +104,13 @@
   
   options ([+] can be repeated):
   
-      --all          fix all non-public non-obsolete revisions
-      --base REV [+] revisions to diff against (overrides automatic selection,
-                     and applies to every revision being fixed)
-   -r --rev REV [+]  revisions to fix
-   -w --working-dir  fix the working directory
-      --whole        always fix every line of a file
+      --all            fix all non-public non-obsolete revisions
+      --base REV [+]   revisions to diff against (overrides automatic selection,
+                       and applies to every revision being fixed)
+   -r --rev REV [+]    revisions to fix
+   -s --source REV [+] fix the specified revisions and their descendants
+   -w --working-dir    fix the working directory
+      --whole          always fix every line of a file
   
   (some details hidden, use --verbose to show complete help)