[PATCH 1 of 3 STABLE] merge: while checking for unknown files don't follow symlinks (issue5027)

[Augie Fackler]

On Mon, Dec 28, 2015 at 10:55:25PM -0800, Siddharth Agarwal wrote:
> # HG changeset patch
> # User Siddharth Agarwal <sid0 at fb.com>
> # Date 1451371897 28800
> #      Mon Dec 28 22:51:37 2015 -0800
> # Branch stable
> # Node ID 5e44604d31266e416de244171ab71df60ff8fd96
> # Parent  1be02894dd6fdc489b90c784456f82d8e7f95178
> # Available At http://42.netv6.net/sid0-wip/hg/
> #              hg pull http://42.netv6.net/sid0-wip/hg/ -r 5e44604d3126
> merge: while checking for unknown files don't follow symlinks (issue5027)

This looks unambiguously correct. Queued for stable.

>
> Previously, we were using Python's native 'os.path.isfile' method which follows
> symlinks. In this case, since we're operating on repo contents, we don't want
> to follow symlinks.
>
> There's a behaviour change here, as shown by the second part of the added test.
> Consider a symlink 'f' pointing to a file containing 'abc'. If we try and
> replace it with a file with contents 'abc', previously we would have let it
> though. Now we don't. Although this breaks naive inspection with tools like
> 'cat' and 'diff', on balance I believe this is the right change.
>
> diff --git a/mercurial/merge.py b/mercurial/merge.py
> --- a/mercurial/merge.py
> +++ b/mercurial/merge.py
> @@ -404,7 +404,7 @@ class mergestate(object):
>  def _checkunknownfile(repo, wctx, mctx, f, f2=None):
>      if f2 is None:
>          f2 = f
> -    return (os.path.isfile(repo.wjoin(f))
> +    return (repo.wvfs.isfileorlink(f)
>          and repo.wvfs.audit.check(f)
>          and repo.dirstate.normalize(f) not in repo.dirstate
>          and mctx[f2].cmp(wctx[f]))
> diff --git a/mercurial/scmutil.py b/mercurial/scmutil.py
> --- a/mercurial/scmutil.py
> +++ b/mercurial/scmutil.py
> @@ -312,6 +312,17 @@ class abstractvfs(object):
>      def islink(self, path=None):
>          return os.path.islink(self.join(path))
>
> +    def isfileorlink(self, path=None):
> +        '''return whether path is a regular file or a symlink
> +
> +        Unlike isfile, this doesn't follow symlinks.'''
> +        try:
> +            st = self.lstat(path)
> +        except OSError:
> +            return False
> +        mode = st.st_mode
> +        return stat.S_ISREG(mode) or stat.S_ISLNK(mode)
> +
>      def reljoin(self, *paths):
>          """join various elements of a path together (as os.path.join would do)
>
> diff --git a/tests/test-merge1.t b/tests/test-merge1.t
> --- a/tests/test-merge1.t
> +++ b/tests/test-merge1.t
> @@ -102,6 +102,28 @@ merge should fail
>    b: untracked file differs
>    abort: untracked files in working directory differ from files in requested revision
>    [255]
> +
> +#if symlink
> +symlinks to directories should be treated as regular files (issue5027)
> +  $ rm b
> +  $ ln -s 'This is file b2' b
> +  $ hg merge 1
> +  b: untracked file differs
> +  abort: untracked files in working directory differ from files in requested revision
> +  [255]
> +symlinks shouldn't be followed
> +  $ rm b
> +  $ echo This is file b1 > .hg/b
> +  $ ln -s .hg/b b
> +  $ hg merge 1
> +  b: untracked file differs
> +  abort: untracked files in working directory differ from files in requested revision
> +  [255]
> +
> +  $ rm b
> +  $ echo This is file b2 > b
> +#endif
> +
>  merge of b expected
>    $ hg merge -f 1
>    merging b
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