fix: add a -s option to format a revision and its descendants

`hg fix -r abc123` will format that commit but not its
descendants. That seems expected given the option name (`-r`), but
it's very rarely what the user wants to do. The problem is that any
descendants of that commit will not be formatted, leaving them as
orphans that are hard to evolve. They are hard to evolve because the
new parent will have formatting changes that the orphan doesn't have.

I talked to Danny Hooper (who wrote most of the fix extension) about
the problem and we agreed that deprecating `-r` in favor of a new `-s`
argument (mimicing rebase's `-s`) would be a good way of reducing the
risk that users end up with these hard-to-evolve orphans. So that's
what this patch implements.

Differential Revision: https://phab.mercurial-scm.org/D8287

hgext/fix.py

@@ -214,6 +214,13 b' baseopt = ('
     _(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 b" usage = _(b'[OPTION]... [FILE]...')"
 
 @command(
     b'fix',
-    [allopt, baseopt, revopt, wdiropt, wholeopt],
+    [allopt, baseopt, revopt, sourceopt, wdiropt, wholeopt],
     usage,
     helpcategory=command.CATEGORY_FILE_CONTENTS,
 )
@@ -249,8 +256,10 b' def fix(ui, repo, *pats, **opts):'
     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_incompatible_arguments(opts, b'working_dir', [b'all'])
+    cmdutil.check_at_most_one_arg(opts, b'all', b'source', b'rev')
+    cmdutil.check_incompatible_arguments(
+        opts, b'working_dir', [b'all', b'source']
+    )
 
     with repo.wlock(), repo.lock(), repo.transaction(b'fix'):
         revstofix = getrevstofix(ui, repo, opts)
@@ -399,6 +408,14 b' def getrevstofix(ui, repo, opts):'
     """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'):

tests/test-fix-topology.t

@@ -21,6 +21,7 b' relationships. We indicate fixed file co'
   $ cat >> $HGRCPATH <<EOF
   > [extensions]
   > fix =
+  > strip =
   > [fix]
   > uppercase-whole-file:command="$PYTHON" $UPPERCASEPY
   > uppercase-whole-file:pattern=set:**
@@ -262,6 +263,111 b' Change A was never a baserev because non'
 
   $ 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

tests/test-fix.t

@@ -108,6 +108,7 b' Help text for fix.'
       --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