filemerge: add support for partial conflict resolution by external tool
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.
Differential Revision: https://phab.mercurial-scm.org/D12356
$ . "$TESTDIR/narrow-library.sh"
$ hg init master
$ cd master
$ mkdir inside
$ echo inside > inside/f1
$ mkdir outside
$ echo outside > outside/f2
$ mkdir patchdir
$ echo patch_this > patchdir/f3
$ hg ci -Aqm 'initial'
$ cd ..
$ hg clone --narrow ssh://user@dummy/master narrow --include inside
requesting all changes
adding changesets
adding manifests
adding file changes
added 1 changesets with 1 changes to 1 files
new changesets dff6a2a6d433
updating to branch default
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ cd narrow
$ mkdir outside
$ echo other_contents > outside/f2
$ hg tracked | grep outside
[1]
$ hg files | grep outside
[1]
$ hg status
`hg status` did not add outside.
$ hg tracked | grep outside
[1]
$ hg files | grep outside
[1]
Unfortunately this is not really a candidate for adding to narrowhg proper,
since it depends on some other source for providing the manifests (when using
treemanifests) and file contents. Something like a virtual filesystem and/or
remotefilelog. We want to be useful when not using those systems, so we do not
have this method available in narrowhg proper at the moment.
$ cat > "$TESTTMP/expand_extension.py" <<EOF
> import os
> import sys
>
> from mercurial import encoding
> from mercurial import extensions
> from mercurial import localrepo
> from mercurial import match as matchmod
> from mercurial import narrowspec
> from mercurial import patch
> from mercurial import util as hgutil
>
> narrowspecexpanded = False
> def expandnarrowspec(ui, repo, newincludes=None):
> if not newincludes:
> return
> if getattr(repo, '_narrowspecexpanded', False):
> return
> repo._narrowspecexpanded = True
> import sys
> newincludes = set([newincludes])
> includes, excludes = repo.narrowpats
> currentmatcher = narrowspec.match(repo.root, includes, excludes)
> includes = includes | newincludes
> if not repo.currenttransaction():
> ui.develwarn(b'expandnarrowspec called outside of transaction!')
> repo.setnarrowpats(includes, excludes)
> narrowspec.copytoworkingcopy(repo)
> newmatcher = narrowspec.match(repo.root, includes, excludes)
> added = matchmod.differencematcher(newmatcher, currentmatcher)
> with repo.dirstate.parentchange():
> for f in repo[b'.'].manifest().walk(added):
> repo.dirstate.update_file(
> f,
> p1_tracked=True,
> wc_tracked=True,
> possibly_dirty=True,
> )
>
> def reposetup(ui, repo):
> class expandingrepo(repo.__class__):
> def narrowmatch(self, *args, **kwargs):
> with repo.wlock(), repo.lock(), repo.transaction(
> b'expandnarrowspec'):
> expandnarrowspec(ui, repo,
> encoding.environ.get(b'DIRSTATEINCLUDES'))
> return super(expandingrepo, self).narrowmatch(*args, **kwargs)
> repo.__class__ = expandingrepo
>
> def extsetup(unused_ui):
> def overridepatch(orig, ui, repo, *args, **kwargs):
> with repo.wlock():
> expandnarrowspec(ui, repo, encoding.environ.get(b'PATCHINCLUDES'))
> return orig(ui, repo, *args, **kwargs)
>
> extensions.wrapfunction(patch, b'patch', overridepatch)
> EOF
$ cat >> ".hg/hgrc" <<EOF
> [extensions]
> expand_extension = $TESTTMP/expand_extension.py
> EOF
Since we do not have the ability to rely on a virtual filesystem or
remotefilelog in the test, we just fake it by copying the data from the 'master'
repo.
$ cp -a ../master/.hg/store/data/* .hg/store/data
Do that for patchdir as well.
$ cp -a ../master/patchdir .
`hg status` will now add outside, but not patchdir.
$ DIRSTATEINCLUDES=path:outside hg status
M outside/f2
$ hg tracked | grep outside
I path:outside
$ hg files | grep outside > /dev/null
$ hg tracked | grep patchdir
[1]
$ hg files | grep patchdir
[1]
Get rid of the modification to outside/f2.
$ hg update -C .
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
This patch will not apply cleanly at the moment, so `hg import` will break
$ cat > "$TESTTMP/foo.patch" <<EOF
> --- patchdir/f3
> +++ patchdir/f3
> @@ -1,1 +1,1 @@
> -this should be "patch_this", but its not, so patch fails
> +this text is irrelevant
> EOF
$ PATCHINCLUDES=path:patchdir hg import -p0 -e "$TESTTMP/foo.patch" -m ignored
applying $TESTTMP/foo.patch
patching file patchdir/f3
Hunk #1 FAILED at 0
1 out of 1 hunks FAILED -- saving rejects to file patchdir/f3.rej
abort: patch failed to apply
[20]
$ hg tracked | grep patchdir
[1]
$ hg files | grep patchdir > /dev/null
[1]
Let's make it apply cleanly and see that it *did* expand properly
$ cat > "$TESTTMP/foo.patch" <<EOF
> --- patchdir/f3
> +++ patchdir/f3
> @@ -1,1 +1,1 @@
> -patch_this
> +patched_this
> EOF
$ PATCHINCLUDES=path:patchdir hg import -p0 -e "$TESTTMP/foo.patch" -m message
applying $TESTTMP/foo.patch
$ cat patchdir/f3
patched_this
$ hg tracked | grep patchdir
I path:patchdir
$ hg files | grep patchdir > /dev/null