Patchwork D12356: filemerge: add support for partial conflict resolution by external tool

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Submitter phabricator
Date March 4, 2022, 9:09 p.m.
Message ID <differential-rev-PHID-DREV-ksxudqh6q4e6zijywyhd-req@mercurial-scm.org>
Download mbox | patch
Permalink /patch/50697/
State New
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phabricator - March 4, 2022, 9:09 p.m.
martinvonz created this revision.
Herald added a reviewer: hg-reviewers.
Herald added a subscriber: mercurial-patches.

REVISION SUMMARY
  A common class of merge conflicts is in imports/#includes/etc. It's
  relatively easy to write a tool that can resolve these conflicts,
  perhaps by naively just unioning the statements and leaving any
  cleanup to other tools to do later [1]. Such specialized tools cannot
  generally resolve all conflicts in a file, of course. Let's therefore
  call them "partial merge tools". Note that the internal simplemerge
  algorithm is such a partial merge tool - one that only resolves
  trivial "conflicts" where one side is unchanged or both sides change
  in the same way.
  
  One can also imagine having smarter language-aware partial tools that
  merge the AST. It may be useful for such tools to interactively let
  the user resolve any conflicts it can't resolve itself. However,
  having the option of implementing it as a partial merge tool means
  that the developer doesn't *need* to create a UI for it. Instead, the
  user can resolve any remaining conflicts with their regular merge tool
  (e.g. `:merge3` or `meld).
  
  We don't currently have a way to let the user define such partial
  merge tools. That's what this patch addresses. It lets the user
  configure partial merge tools to run. Each tool can be configured to
  run only on files matching certain patterns (e.g. "*.py"). The tool
  takes three inputs (local, base, other) and resolves conflicts by
  updating these in place. For example, let's say the inputs are these:
  
  base:
  
    import sys
    
    def main():
      print('Hello')
  
  local:
  
    import os
    import sys
    
    def main():
      print('Hi')
  
  other:
  
    import re
    import sys
    
    def main():
      print('Howdy')
  
  A partial merge tool could now resolve the conflicting imports by
  replacing the import statements in *all* files by the following
  snippet, while leaving the remainder of the files unchanged.
  
    import os
    import re
    import sys
  
  As a result, simplemerge and any regular merge tool that runs after
  the partial merge tool(s) will consider the imports to be
  non-conflicting and will only present the conflict in `main()` to the
  user.

REPOSITORY
  rHG Mercurial

BRANCH
  default

REVISION DETAIL
  https://phab.mercurial-scm.org/D12356

AFFECTED FILES
  mercurial/configitems.py
  mercurial/filemerge.py
  mercurial/simplemerge.py
  tests/test-merge-partial-tool.t

CHANGE DETAILS




To: martinvonz, #hg-reviewers
Cc: mercurial-patches, mercurial-devel

Patch

diff --git a/tests/test-merge-partial-tool.t b/tests/test-merge-partial-tool.t
new file mode 100644
--- /dev/null
+++ b/tests/test-merge-partial-tool.t
@@ -0,0 +1,209 @@ 
+Test support for partial-resolution tools
+
+Create a tool that resolves conflicts after line 5 by simply dropping those
+lines (even if there are no conflicts there)
+  $ cat >> "$TESTTMP/head.sh" <<'EOF'
+  > #!/bin/sh
+  > for f in "$@"; do
+  >   head -5 $f > tmp
+  >   mv -f tmp $f
+  > done
+  > EOF
+  $ chmod +x "$TESTTMP/head.sh"
+...and another tool that keeps only the last 5 lines instead of the first 5.
+  $ cat >> "$TESTTMP/tail.sh" <<'EOF'
+  > #!/bin/sh
+  > for f in "$@"; do
+  >   tail -5 $f > tmp
+  >   mv -f tmp $f
+  > done
+  > EOF
+  $ chmod +x "$TESTTMP/tail.sh"
+
+Set up both tools to run on all patterns (the default), and let the `tail` tool
+run after the `head` tool, which means it will have no effect (we'll override it
+to test order later)
+  $ cat >> "$HGRCPATH" <<EOF
+  > [partial-merge-tools]
+  > head.executable=$TESTTMP/head.sh
+  > tail.executable=$TESTTMP/tail.sh
+  > tail.order=1
+  > EOF
+
+  $ make_commit() {
+  >   echo "$@" | xargs -n1 > file
+  >   hg add file 2> /dev/null
+  >   hg ci -m "$*"
+  > }
+
+
+Let a partial-resolution tool resolve some conflicts and leave other conflicts
+for the regular merge tool (:merge3 here)
+
+  $ hg init repo
+  $ cd repo
+  $ make_commit a b c d e f
+  $ make_commit a b2 c d e f2
+  $ hg co 0
+  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  $ make_commit a b3 c d e f3
+  created new head
+  $ hg merge 1 -t :merge3
+  merging file
+  warning: conflicts while merging file! (edit, then use 'hg resolve --mark')
+  0 files updated, 0 files merged, 0 files removed, 1 files unresolved
+  use 'hg resolve' to retry unresolved file merges or 'hg merge --abort' to abandon
+  [1]
+  $ cat file
+  a
+  <<<<<<< working copy:    e11a49d4b620 - test: a b3 c d e f3
+  b3
+  ||||||| common ancestor: 8ae8bb9cc43a - test: a b c d e f
+  b
+  =======
+  b2
+  >>>>>>> merge rev:       fbc096a40cc5 - test: a b2 c d e f2
+  c
+  d
+  e
+
+
+With premerge=keep, the partial-resolution tools runs before and doesn't see
+the conflict markers
+
+  $ hg co -C 2
+  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  $ cat >> .hg/hgrc <<EOF
+  > [merge-tools]
+  > my-local.executable = cat
+  > my-local.args = $local
+  > my-local.premerge = keep-merge3
+  > EOF
+  $ hg merge 1 -t my-local
+  merging file
+  0 files updated, 1 files merged, 0 files removed, 0 files unresolved
+  (branch merge, don't forget to commit)
+  $ cat file
+  a
+  <<<<<<< working copy:    e11a49d4b620 - test: a b3 c d e f3
+  b3
+  ||||||| common ancestor: 8ae8bb9cc43a - test: a b c d e f
+  b
+  =======
+  b2
+  >>>>>>> merge rev:       fbc096a40cc5 - test: a b2 c d e f2
+  c
+  d
+  e
+
+
+When a partial-resolution tool resolves all conflicts, the resolution should
+be recorded and the regular merge tool should not be invoked for the file.
+
+  $ hg co -C 0
+  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  $ make_commit a b c d e f2
+  created new head
+  $ hg co 0
+  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  $ make_commit a b c d e f3
+  created new head
+  $ hg merge 3 -t false
+  merging file
+  0 files updated, 1 files merged, 0 files removed, 0 files unresolved
+  (branch merge, don't forget to commit)
+  $ cat file
+  a
+  b
+  c
+  d
+  e
+
+
+Only tools whose patterns match are run. We make `head` not match here, so
+only `tail` should run
+
+  $ hg co -C 4
+  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  $ hg merge 3 -t :merge3 --config partial-merge-tools.head.patterns=other
+  merging file
+  warning: conflicts while merging file! (edit, then use 'hg resolve --mark')
+  0 files updated, 0 files merged, 0 files removed, 1 files unresolved
+  use 'hg resolve' to retry unresolved file merges or 'hg merge --abort' to abandon
+  [1]
+  $ cat file
+  b
+  c
+  d
+  e
+  <<<<<<< working copy:    d57edaa6e21a - test: a b c d e f3
+  f3
+  ||||||| common ancestor: 8ae8bb9cc43a - test: a b c d e f
+  f
+  =======
+  f2
+  >>>>>>> merge rev:       8c217da987be - test: a b c d e f2
+
+
+If there are several matching tools, they are run in requested order. We move
+`head` after `tail` in order here so it has no effect (the conflict in "f" thus
+remains).
+
+  $ hg co -C 4
+  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  $ hg merge 3 -t :merge3 --config partial-merge-tools.head.order=2
+  merging file
+  warning: conflicts while merging file! (edit, then use 'hg resolve --mark')
+  0 files updated, 0 files merged, 0 files removed, 1 files unresolved
+  use 'hg resolve' to retry unresolved file merges or 'hg merge --abort' to abandon
+  [1]
+  $ cat file
+  b
+  c
+  d
+  e
+  <<<<<<< working copy:    d57edaa6e21a - test: a b c d e f3
+  f3
+  ||||||| common ancestor: 8ae8bb9cc43a - test: a b c d e f
+  f
+  =======
+  f2
+  >>>>>>> merge rev:       8c217da987be - test: a b c d e f2
+
+
+When using "nomerge" tools (e.g. `:other`), the partial-resolution tools
+should not be run.
+
+  $ hg co -C 4
+  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  $ hg merge 3 -t :other
+  0 files updated, 1 files merged, 0 files removed, 0 files unresolved
+  (branch merge, don't forget to commit)
+  $ cat file
+  a
+  b
+  c
+  d
+  e
+  f2
+
+
+If a partial-resolution tool resolved some conflict and simplemerge can
+merge the rest, then the regular merge tool should not be used. Here we merge
+"a b c d e3 f3" with "a b2 c d e f2". The `head` tool resolves the conflict in
+"f" and the internal simplemerge merges the remaining changes in "b" and "e".
+
+  $ hg co -C 0
+  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  $ make_commit a b c d e3 f3
+  created new head
+  $ hg merge 1 -t false
+  merging file
+  0 files updated, 1 files merged, 0 files removed, 0 files unresolved
+  (branch merge, don't forget to commit)
+  $ cat file
+  a
+  b2
+  c
+  d
+  e3
diff --git a/mercurial/simplemerge.py b/mercurial/simplemerge.py
--- a/mercurial/simplemerge.py
+++ b/mercurial/simplemerge.py
@@ -490,6 +490,9 @@ 
             self._text = self.fctx.decodeddata()
         return self._text
 
+    def set_text(self, text):
+        self._text = text
+
 
 def simplemerge(
     local,
diff --git a/mercurial/filemerge.py b/mercurial/filemerge.py
--- a/mercurial/filemerge.py
+++ b/mercurial/filemerge.py
@@ -1052,6 +1052,7 @@ 
             markerstyle = internalmarkerstyle
 
         if mergetype == fullmerge:
+            _run_partial_resolution_tools(repo, local, other, base)
             # conflict markers generated by premerge will use 'detailed'
             # settings if either ui.mergemarkers or the tool's mergemarkers
             # setting is 'detailed'. This way tools can have basic labels in
@@ -1116,6 +1117,59 @@ 
             backup.remove()
 
 
+def _run_partial_resolution_tools(repo, local, other, base):
+    """Runs partial-resolution tools on the three inputs and updates them."""
+    ui = repo.ui
+    # Tuples of (order, name, executable path)
+    tools = []
+    seen = set()
+    section = b"partial-merge-tools"
+    for k, v in ui.configitems(section):
+        name = k.split(b'.')[0]
+        if name in seen:
+            continue
+        patterns = ui.configlist(section, b'%s.patterns' % name, [b'.'])
+        m = match.match(repo.root, b'', patterns)
+        if m(local.fctx.path()):
+            order = ui.configint(section, b'%s.order' % name, 0)
+            executable = ui.config(section, b'%s.executable' % name, name)
+            tools.append((order, name, executable))
+
+    if not tools:
+        return
+    # Sort in configured order (first in tuple)
+    tools.sort()
+
+    files = [
+        (b"local", local.fctx.path(), local.text()),
+        (b"base", base.fctx.path(), base.text()),
+        (b"other", other.fctx.path(), other.text()),
+    ]
+
+    with _maketempfiles(files) as temppaths:
+        localpath, basepath, otherpath = temppaths
+
+        for order, name, executable in tools:
+            cmd = procutil.shellquote(executable)
+            # TODO: Allow the user to configure the command line using
+            # $local, $base, $other.
+            cmd = b'%s %s %s %s' % (cmd, localpath, basepath, otherpath)
+            r = ui.system(cmd, cwd=repo.root, blockedtag=b'partial-mergetool')
+            if r:
+                raise error.StateError(
+                    b'partial merge tool %s exited with code %d' % (name, r)
+                )
+            local_text = util.readfile(localpath)
+            other_text = util.readfile(otherpath)
+            if local_text == other_text:
+                # No need to run other tools if all conflicts have been resolved
+                break
+
+        local.set_text(local_text)
+        base.set_text(util.readfile(basepath))
+        other.set_text(other_text)
+
+
 def _haltmerge():
     msg = _(b'merge halted after failed merge (see hg resolve)')
     raise error.InterventionRequired(msg)
diff --git a/mercurial/configitems.py b/mercurial/configitems.py
--- a/mercurial/configitems.py
+++ b/mercurial/configitems.py
@@ -1570,6 +1570,37 @@ 
     default=False,
 )
 coreconfigitem(
+    b'partial-merge-tools',
+    b'.*',
+    default=None,
+    generic=True,
+    experimental=True,
+)
+coreconfigitem(
+    b'partial-merge-tools',
+    br'.*\.patterns',
+    default=dynamicdefault,
+    generic=True,
+    priority=-1,
+    experimental=True,
+)
+coreconfigitem(
+    b'partial-merge-tools',
+    br'.*\.executable$',
+    default=dynamicdefault,
+    generic=True,
+    priority=-1,
+    experimental=True,
+)
+coreconfigitem(
+    b'partial-merge-tools',
+    br'.*\.order',
+    default=0,
+    generic=True,
+    priority=-1,
+    experimental=True,
+)
+coreconfigitem(
     b'merge-tools',
     b'.*',
     default=None,