extdiff: avoid unexpected quoting arguments for external tools (issue4463)

Before this patch, all command line arguments for external tools are
quoted by the combination of "shlex.split" and "util.shellquote". But
this causes some problems.

  - some problematic commands can't work correctly with quoted arguments

    For example, 'WinMerge /r ....' is OK, but 'WinMerge "/r" ....' is
    NG. See also below for detail about this problem.

        https://bitbucket.org/tortoisehg/thg/issue/3978/

  - quoting itself may change semantics of arguments

    For example, when the environment variable CONCAT="foo bar baz':

      - mydiff $CONCAT   => mydiff foo bar baz   (taking 3 arguments)
      - mydiff "$CONCAT" => mydiff "foo bar baz" (taking only 1 argument)

    For another example, single quoting (= "util.shellquote") on POSIX
    environment prevents shells from expanding environment variables,
    tilde, and so on:

      - mydiff "$HOME" => mydiff /home/foobar
      - mydiff '$HOME' => mydiff $HOME

  - "shlex.split" can't handle some special characters correctly

    It just splits specified command line by whitespaces.

    For example, "echo foo;echo bar" is split into ["echo",
    "foo;echo", "bar"].

On the other hand, if quoting itself is omitted, users can't specify
options including space characters with "--option" at runtime.

The root cause of this issue is that "shlex.split + util.shellquote"
combination loses whether users really want to quote each command line
elements or not, even though these can be quoted arbitrarily in
configurations.

To resolve this problem, this patch does:

  - prevent configurations from being processed by "shlex.split" and
    "util.shellquote"

    only (possibly) "findexe"-ed or "findexternaltool"-ed command path
    is "util.shellquote", because it may contain whitespaces.

  - quote options specified by "--option" via command line at runtime

This patch also makes "dodiff()" take only one "args" argument instead
of "diffcmd" and "diffopts. It also omits applying "util.shellquote"
on "args", because "args" should be already stringified in "extdiff()"
and "mydiff()".

The last hunk for "test-extdiff.t" replaces two whitespaces by single
whitespace, because change of "' '.join()" logic causes omitting
redundant whitespaces.

hgext/extdiff.py

@@ -1,330 +1,337 b''
 # extdiff.py - external diff program support for mercurial
 #
 # Copyright 2006 Vadim Gelfer <[e-mail]>
 #
 # This software may be used and distributed according to the terms of the
 # GNU General Public License version 2 or any later version.
 
 '''command to allow external programs to compare revisions
 
 The extdiff Mercurial extension allows you to use external programs
 to compare revisions, or revision with working directory. The external
 diff programs are called with a configurable set of options and two
 non-option arguments: paths to directories containing snapshots of
 files to compare.
 
 The extdiff extension also allows you to configure new diff commands, so
 you do not need to type :hg:`extdiff -p kdiff3` always. ::
 
   [extdiff]
   # add new command that runs GNU diff(1) in 'context diff' mode
   cdiff = gdiff -Nprc5
   ## or the old way:
   #cmd.cdiff = gdiff
   #opts.cdiff = -Nprc5
 
   # add new command called meld, runs meld (no need to name twice).  If
   # the meld executable is not available, the meld tool in [merge-tools]
   # will be used, if available
   meld =
 
   # add new command called vimdiff, runs gvimdiff with DirDiff plugin
   # (see http://www.vim.org/scripts/script.php?script_id=102) Non
   # English user, be sure to put "let g:DirDiffDynamicDiffText = 1" in
   # your .vimrc
   vimdiff = gvim -f "+next" \\
             "+execute 'DirDiff' fnameescape(argv(0)) fnameescape(argv(1))"
 
 Tool arguments can include variables that are expanded at runtime::
 
   $parent1, $plabel1 - filename, descriptive label of first parent
   $child,   $clabel  - filename, descriptive label of child revision
   $parent2, $plabel2 - filename, descriptive label of second parent
   $root              - repository root
   $parent is an alias for $parent1.
 
 The extdiff extension will look in your [diff-tools] and [merge-tools]
 sections for diff tool arguments, when none are specified in [extdiff].
 
 ::
 
   [extdiff]
   kdiff3 =
 
   [diff-tools]
   kdiff3.diffargs=--L1 '$plabel1' --L2 '$clabel' $parent $child
 
 You can use -I/-X and list of file or directory names like normal
 :hg:`diff` command. The extdiff extension makes snapshots of only
 needed files, so running the external diff program will actually be
 pretty fast (at least faster than having to compare the entire tree).
 '''
 
 from mercurial.i18n import _
 from mercurial.node import short, nullid
 from mercurial import cmdutil, scmutil, util, commands, encoding, filemerge
 import os, shlex, shutil, tempfile, re
 
 cmdtable = {}
 command = cmdutil.command(cmdtable)
 testedwith = 'internal'
 
 def snapshot(ui, repo, files, node, tmproot):
     '''snapshot files as of some revision
     if not using snapshot, -I/-X does not work and recursive diff
     in tools like kdiff3 and meld displays too many files.'''
     dirname = os.path.basename(repo.root)
     if dirname == "":
         dirname = "root"
     if node is not None:
         dirname = '%s.%s' % (dirname, short(node))
     base = os.path.join(tmproot, dirname)
     os.mkdir(base)
     if node is not None:
         ui.note(_('making snapshot of %d files from rev %s\n') %
                 (len(files), short(node)))
     else:
         ui.note(_('making snapshot of %d files from working directory\n') %
             (len(files)))
     wopener = scmutil.opener(base)
     fns_and_mtime = []
     ctx = repo[node]
     for fn in sorted(files):
         wfn = util.pconvert(fn)
         if wfn not in ctx:
             # File doesn't exist; could be a bogus modify
             continue
         ui.note('  %s\n' % wfn)
         dest = os.path.join(base, wfn)
         fctx = ctx[wfn]
         data = repo.wwritedata(wfn, fctx.data())
         if 'l' in fctx.flags():
             wopener.symlink(data, wfn)
         else:
             wopener.write(wfn, data)
             if 'x' in fctx.flags():
                 util.setflags(dest, False, True)
         if node is None:
             fns_and_mtime.append((dest, repo.wjoin(fn),
                                   os.lstat(dest).st_mtime))
     return dirname, fns_and_mtime
 
-def dodiff(ui, repo, diffcmd, diffopts, pats, opts):
+def dodiff(ui, repo, args, pats, opts):
     '''Do the actual diff:
 
     - copy to a temp structure if diffing 2 internal revisions
     - copy to a temp structure if diffing working revision with
       another one and more than 1 file is changed
     - just invoke the diff for a single file in the working dir
     '''
 
     revs = opts.get('rev')
     change = opts.get('change')
-    args = ' '.join(map(util.shellquote, diffopts))
     do3way = '$parent2' in args
 
     if revs and change:
         msg = _('cannot specify --rev and --change at the same time')
         raise util.Abort(msg)
     elif change:
         node2 = scmutil.revsingle(repo, change, None).node()
         node1a, node1b = repo.changelog.parents(node2)
     else:
         node1a, node2 = scmutil.revpair(repo, revs)
         if not revs:
             node1b = repo.dirstate.p2()
         else:
             node1b = nullid
 
     # Disable 3-way merge if there is only one parent
     if do3way:
         if node1b == nullid:
             do3way = False
 
     matcher = scmutil.match(repo[node2], pats, opts)
     mod_a, add_a, rem_a = map(set, repo.status(node1a, node2, matcher)[:3])
     if do3way:
         mod_b, add_b, rem_b = map(set, repo.status(node1b, node2, matcher)[:3])
     else:
         mod_b, add_b, rem_b = set(), set(), set()
     modadd = mod_a | add_a | mod_b | add_b
     common = modadd | rem_a | rem_b
     if not common:
         return 0
 
     tmproot = tempfile.mkdtemp(prefix='extdiff.')
     try:
         # Always make a copy of node1a (and node1b, if applicable)
         dir1a_files = mod_a | rem_a | ((mod_b | add_b) - add_a)
         dir1a = snapshot(ui, repo, dir1a_files, node1a, tmproot)[0]
         rev1a = '@%d' % repo[node1a].rev()
         if do3way:
             dir1b_files = mod_b | rem_b | ((mod_a | add_a) - add_b)
             dir1b = snapshot(ui, repo, dir1b_files, node1b, tmproot)[0]
             rev1b = '@%d' % repo[node1b].rev()
         else:
             dir1b = None
             rev1b = ''
 
         fns_and_mtime = []
 
         # If node2 in not the wc or there is >1 change, copy it
         dir2root = ''
         rev2 = ''
         if node2:
             dir2 = snapshot(ui, repo, modadd, node2, tmproot)[0]
             rev2 = '@%d' % repo[node2].rev()
         elif len(common) > 1:
             #we only actually need to get the files to copy back to
             #the working dir in this case (because the other cases
             #are: diffing 2 revisions or single file -- in which case
             #the file is already directly passed to the diff tool).
             dir2, fns_and_mtime = snapshot(ui, repo, modadd, None, tmproot)
         else:
             # This lets the diff tool open the changed file directly
             dir2 = ''
             dir2root = repo.root
 
         label1a = rev1a
         label1b = rev1b
         label2 = rev2
 
         # If only one change, diff the files instead of the directories
         # Handle bogus modifies correctly by checking if the files exist
         if len(common) == 1:
             common_file = util.localpath(common.pop())
             dir1a = os.path.join(tmproot, dir1a, common_file)
             label1a = common_file + rev1a
             if not os.path.isfile(dir1a):
                 dir1a = os.devnull
             if do3way:
                 dir1b = os.path.join(tmproot, dir1b, common_file)
                 label1b = common_file + rev1b
                 if not os.path.isfile(dir1b):
                     dir1b = os.devnull
             dir2 = os.path.join(dir2root, dir2, common_file)
             label2 = common_file + rev2
 
         # Function to quote file/dir names in the argument string.
         # When not operating in 3-way mode, an empty string is
         # returned for parent2
         replace = {'parent': dir1a, 'parent1': dir1a, 'parent2': dir1b,
                    'plabel1': label1a, 'plabel2': label1b,
                    'clabel': label2, 'child': dir2,
                    'root': repo.root}
         def quote(match):
             key = match.group()[1:]
             if not do3way and key == 'parent2':
                 return ''
             return util.shellquote(replace[key])
 
         # Match parent2 first, so 'parent1?' will match both parent1 and parent
         regex = '\$(parent2|parent1?|child|plabel1|plabel2|clabel|root)'
         if not do3way and not re.search(regex, args):
             args += ' $parent1 $child'
-        args = re.sub(regex, quote, args)
-        cmdline = util.shellquote(diffcmd) + ' ' + args
+        cmdline = re.sub(regex, quote, args)
 
         ui.debug('running %r in %s\n' % (cmdline, tmproot))
         ui.system(cmdline, cwd=tmproot)
 
         for copy_fn, working_fn, mtime in fns_and_mtime:
             if os.lstat(copy_fn).st_mtime != mtime:
                 ui.debug('file changed while diffing. '
                          'Overwriting: %s (src: %s)\n' % (working_fn, copy_fn))
                 util.copyfile(copy_fn, working_fn)
 
         return 1
     finally:
         ui.note(_('cleaning up temp directory\n'))
         shutil.rmtree(tmproot)
 
 @command('extdiff',
     [('p', 'program', '',
      _('comparison program to run'), _('CMD')),
     ('o', 'option', [],
      _('pass option to comparison program'), _('OPT')),
     ('r', 'rev', [], _('revision'), _('REV')),
     ('c', 'change', '', _('change made by revision'), _('REV')),
     ] + commands.walkopts,
     _('hg extdiff [OPT]... [FILE]...'),
     inferrepo=True)
 def extdiff(ui, repo, *pats, **opts):
     '''use external program to diff repository (or selected files)
 
     Show differences between revisions for the specified files, using
     an external program. The default program used is diff, with
     default options "-Npru".
 
     To select a different program, use the -p/--program option. The
     program will be passed the names of two directories to compare. To
     pass additional options to the program, use -o/--option. These
     will be passed before the names of the directories to compare.
 
     When two revision arguments are given, then changes are shown
     between those revisions. If only one revision is specified then
     that revision is compared to the working directory, and, when no
     revisions are specified, the working directory files are compared
     to its parent.'''
     program = opts.get('program')
     option = opts.get('option')
     if not program:
         program = 'diff'
         option = option or ['-Npru']
-    return dodiff(ui, repo, program, option, pats, opts)
+    cmdline = ' '.join(map(util.shellquote, [program] + option))
+    return dodiff(ui, repo, cmdline, pats, opts)
 
 def uisetup(ui):
     for cmd, path in ui.configitems('extdiff'):
         if cmd.startswith('cmd.'):
             cmd = cmd[4:]
             if not path:
                 path = util.findexe(cmd)
                 if path is None:
                     path = filemerge.findexternaltool(ui, cmd) or cmd
-            diffopts = shlex.split(ui.config('extdiff', 'opts.' + cmd, ''))
+            diffopts = ui.config('extdiff', 'opts.' + cmd, '')
+            cmdline = util.shellquote(path)
+            if diffopts:
+                cmdline += ' ' + diffopts
         elif cmd.startswith('opts.'):
             continue
         else:
-            # command = path opts
             if path:
-                diffopts = shlex.split(path)
-                path = diffopts.pop(0)
+                # case "cmd = path opts"
+                cmdline = path
+                diffopts = len(shlex.split(cmdline)) > 1
             else:
-                path, diffopts = util.findexe(cmd), []
+                # case "cmd ="
+                path = util.findexe(cmd)
                 if path is None:
                     path = filemerge.findexternaltool(ui, cmd) or cmd
+                cmdline = util.shellquote(path)
+                diffopts = False
         # look for diff arguments in [diff-tools] then [merge-tools]
-        if diffopts == []:
+        if not diffopts:
             args = ui.config('diff-tools', cmd+'.diffargs') or \
                    ui.config('merge-tools', cmd+'.diffargs')
             if args:
-                diffopts = shlex.split(args)
-        def save(cmd, path, diffopts):
+                cmdline += ' ' + args
+        def save(cmdline):
             '''use closure to save diff command to use'''
             def mydiff(ui, repo, *pats, **opts):
-                return dodiff(ui, repo, path, diffopts + opts['option'],
-                              pats, opts)
+                options = ' '.join(map(util.shellquote, opts['option']))
+                if options:
+                    options = ' ' + options
+                return dodiff(ui, repo, cmdline + options, pats, opts)
             doc = _('''\
 use %(path)s to diff repository (or selected files)
 
     Show differences between revisions for the specified files, using
     the %(path)s program.
 
     When two revision arguments are given, then changes are shown
     between those revisions. If only one revision is specified then
     that revision is compared to the working directory, and, when no
     revisions are specified, the working directory files are compared
     to its parent.\
 ''') % {'path': util.uirepr(path)}
 
             # We must translate the docstring right away since it is
             # used as a format string. The string will unfortunately
             # be translated again in commands.helpcmd and this will
             # fail when the docstring contains non-ASCII characters.
             # Decoding the string to a Unicode string here (using the
             # right encoding) prevents that.
             mydiff.__doc__ = doc.decode(encoding.encoding)
             return mydiff
-        cmdtable[cmd] = (save(cmd, path, diffopts),
+        cmdtable[cmd] = (save(cmdline),
                          cmdtable['extdiff'][1][1:],
                          _('hg %s [OPTION]... [FILE]...') % cmd)

tests/test-extdiff.t

@@ -1,236 +1,302 b''
   $ echo "[extensions]" >> $HGRCPATH
   $ echo "extdiff=" >> $HGRCPATH
 
   $ hg init a
   $ cd a
   $ echo a > a
   $ echo b > b
   $ hg add
   adding a
   adding b
 
 Should diff cloned directories:
 
   $ hg extdiff -o -r $opt
   Only in a: a
   Only in a: b
   [1]
 
   $ cat <<EOF >> $HGRCPATH
   > [extdiff]
   > cmd.falabala = echo
   > opts.falabala = diffing
   > cmd.edspace = echo
   > opts.edspace = "name  <[e-mail]>"
   > EOF
 
   $ hg falabala
   diffing a.000000000000 a
   [1]
 
   $ hg help falabala
   hg falabala [OPTION]... [FILE]...
   
   use 'echo' to diff repository (or selected files)
   
       Show differences between revisions for the specified files, using the
       'echo' program.
   
       When two revision arguments are given, then changes are shown between
       those revisions. If only one revision is specified then that revision is
       compared to the working directory, and, when no revisions are specified,
       the working directory files are compared to its parent.
   
   options ([+] can be repeated):
   
    -o --option OPT [+]      pass option to comparison program
    -r --rev REV [+]         revision
    -c --change REV          change made by revision
    -I --include PATTERN [+] include names matching the given patterns
    -X --exclude PATTERN [+] exclude names matching the given patterns
   
   (some details hidden, use --verbose to show complete help)
 
   $ hg ci -d '0 0' -mtest1
 
   $ echo b >> a
   $ hg ci -d '1 0' -mtest2
 
 Should diff cloned files directly:
 
   $ hg falabala -r 0:1
   diffing */extdiff.*/a.8a5febb7f867/a a.34eed99112ab/a (glob)
   [1]
 
 Test diff during merge:
 
   $ hg update -C 0
   1 files updated, 0 files merged, 0 files removed, 0 files unresolved
   $ echo c >> c
   $ hg add c
   $ hg ci -m "new branch" -d '1 0'
   created new head
   $ hg merge 1
   1 files updated, 0 files merged, 0 files removed, 0 files unresolved
   (branch merge, don't forget to commit)
 
 Should diff cloned file against wc file:
 
   $ hg falabala
   diffing */extdiff.*/a.2a13a4d2da36/a */a/a (glob)
   [1]
 
 
 Test --change option:
 
   $ hg ci -d '2 0' -mtest3
   $ hg falabala -c 1
   diffing */extdiff.*/a.8a5febb7f867/a a.34eed99112ab/a (glob)
   [1]
 
 Check diff are made from the first parent:
 
   $ hg falabala -c 3 || echo "diff-like tools yield a non-zero exit code"
   diffing */extdiff.*/a.2a13a4d2da36/a a.46c0e4daeb72/a (glob)
   diff-like tools yield a non-zero exit code
 
+issue4463: usage of command line configuration without additional quoting
+
+  $ cat <<EOF >> $HGRCPATH
+  > [extdiff]
+  > cmd.4463a = echo
+  > opts.4463a = a-naked 'single quoted' "double quoted"
+  > 4463b = echo b-naked 'single quoted' "double quoted"
+  > echo =
+  > EOF
+  $ hg update -q -C 0
+  $ echo a >> a
+#if windows
+  $ hg --debug 4463a | grep '^running'
+  running '"echo" a-naked \'single quoted\' "double quoted" "*\\a" "*\\a"' in */extdiff.* (glob)
+  $ hg --debug 4463b | grep '^running'
+  running 'echo b-naked \'single quoted\' "double quoted" "*\\a" "*\\a"' in */extdiff.* (glob)
+  $ hg --debug echo | grep '^running'
+  running '"*echo*" "*\\a" "*\\a"' in */extdiff.* (glob)
+#else
+  $ hg --debug 4463a | grep '^running'
+  running '\'echo\' a-naked \'single quoted\' "double quoted" \'*/a\' \'$TESTTMP/a/a\'' in */extdiff.* (glob)
+  $ hg --debug 4463b | grep '^running'
+  running 'echo b-naked \'single quoted\' "double quoted" \'*/a\' \'$TESTTMP/a/a\'' in */extdiff.* (glob)
+  $ hg --debug echo | grep '^running'
+  running "'*echo*' '*/a' '$TESTTMP/a/a'" in */extdiff.* (glob)
+#endif
+
+(getting options from other than extdiff section)
+
+  $ cat <<EOF >> $HGRCPATH
+  > [extdiff]
+  > # using diff-tools diffargs
+  > 4463b2 = echo
+  > # using merge-tools diffargs
+  > 4463b3 = echo
+  > # no diffargs
+  > 4463b4 = echo
+  > [diff-tools]
+  > 4463b2.diffargs = b2-naked 'single quoted' "double quoted"
+  > [merge-tools]
+  > 4463b3.diffargs = b3-naked 'single quoted' "double quoted"
+  > EOF
+#if windows
+  $ hg --debug 4463b2 | grep '^running'
+  running 'echo b2-naked \'single quoted\' "double quoted" "*\\a" "*\\a"' in */extdiff.* (glob)
+  $ hg --debug 4463b3 | grep '^running'
+  running 'echo b3-naked \'single quoted\' "double quoted" "*\\a" "*\\a"' in */extdiff.* (glob)
+  $ hg --debug 4463b4 | grep '^running'
+  running 'echo "*\\a" "*\\a"' in */extdiff.* (glob)
+  $ hg --debug 4463b4 --option 'being quoted' | grep '^running'
+  running 'echo "being quoted" "*\\a" "*\\a"' in */extdiff.* (glob)
+  $ hg --debug extdiff -p echo --option 'being quoted' | grep '^running'
+  running '"echo" "being quoted" "*\\a" "*\\a"' in */extdiff.* (glob)
+#else
+  $ hg --debug 4463b2 | grep '^running'
+  running 'echo b2-naked \'single quoted\' "double quoted" \'*/a\' \'$TESTTMP/a/a\'' in */extdiff.* (glob)
+  $ hg --debug 4463b3 | grep '^running'
+  running 'echo b3-naked \'single quoted\' "double quoted" \'*/a\' \'$TESTTMP/a/a\'' in */extdiff.* (glob)
+  $ hg --debug 4463b4 | grep '^running'
+  running "echo '*/a' '$TESTTMP/a/a'" in */extdiff.* (glob)
+  $ hg --debug 4463b4 --option 'being quoted' | grep '^running'
+  running "echo 'being quoted' '*/a' '$TESTTMP/a/a'" in */extdiff.* (glob)
+  $ hg --debug extdiff -p echo --option 'being quoted' | grep '^running'
+  running "'echo' 'being quoted' '*/a' '$TESTTMP/a/a'" in */extdiff.* (glob)
+#endif
+
 #if execbit
 
 Test extdiff of multiple files in tmp dir:
 
   $ hg update -C 0 > /dev/null
   $ echo changed > a
   $ echo changed > b
   $ chmod +x b
 
 Diff in working directory, before:
 
   $ hg diff --git
   diff --git a/a b/a
   --- a/a
   +++ b/a
   @@ -1,1 +1,1 @@
   -a
   +changed
   diff --git a/b b/b
   old mode 100644
   new mode 100755
   --- a/b
   +++ b/b
   @@ -1,1 +1,1 @@
   -b
   +changed
 
 
 Edit with extdiff -p:
 
 Prepare custom diff/edit tool:
 
   $ cat > 'diff tool.py' << EOT
   > #!/usr/bin/env python
   > import time
   > time.sleep(1) # avoid unchanged-timestamp problems
   > file('a/a', 'ab').write('edited\n')
   > file('a/b', 'ab').write('edited\n')
   > EOT
 
   $ chmod +x 'diff tool.py'
 
 will change to /tmp/extdiff.TMP and populate directories a.TMP and a
 and start tool
 
   $ hg extdiff -p "`pwd`/diff tool.py"
   [1]
 
 Diff in working directory, after:
 
   $ hg diff --git
   diff --git a/a b/a
   --- a/a
   +++ b/a
   @@ -1,1 +1,2 @@
   -a
   +changed
   +edited
   diff --git a/b b/b
   old mode 100644
   new mode 100755
   --- a/b
   +++ b/b
   @@ -1,1 +1,2 @@
   -b
   +changed
   +edited
 
 Test extdiff with --option:
 
   $ hg extdiff -p echo -o this -c 1
   this */extdiff.*/a.8a5febb7f867/a a.34eed99112ab/a (glob)
   [1]
 
   $ hg falabala -o this -c 1
   diffing this */extdiff.*/a.8a5febb7f867/a a.34eed99112ab/a (glob)
   [1]
 
 Test extdiff's handling of options with spaces in them:
 
   $ hg edspace -c 1
   name  <[e-mail]> */extdiff.*/a.8a5febb7f867/a a.34eed99112ab/a (glob)
   [1]
 
   $ hg extdiff -p echo -o "name  <[e-mail]>" -c 1
   name  <[e-mail]> */extdiff.*/a.8a5febb7f867/a a.34eed99112ab/a (glob)
   [1]
 
 Test with revsets:
 
   $ hg extdif -p echo -c "rev(1)"
   */extdiff.*/a.8a5febb7f867/a a.34eed99112ab/a (glob)
   [1]
 
   $ hg extdif -p echo -r "0::1"
   */extdiff.*/a.8a5febb7f867/a a.34eed99112ab/a (glob)
   [1]
 
 Fallback to merge-tools.tool.executable|regkey
   $ mkdir dir
   $ cat > 'dir/tool.sh' << EOF
   > #!/bin/sh
   > echo "** custom diff **"
   > EOF
   $ chmod +x dir/tool.sh
   $ tool=`pwd`/dir/tool.sh
   $ hg --debug tl --config extdiff.tl= --config merge-tools.tl.executable=$tool
   making snapshot of 2 files from rev * (glob)
     a
     b
   making snapshot of 2 files from working directory
     a
     b
   running "'$TESTTMP/a/dir/tool.sh'  'a.*' 'a'" in */extdiff.* (glob)
   ** custom diff **
   cleaning up temp directory
   [1]
 
   $ cd ..
 
 #endif
 
 #if symlink
 
 Test symlinks handling (issue1909)
 
   $ hg init testsymlinks
   $ cd testsymlinks
   $ echo a > a
   $ hg ci -Am adda
   adding a
   $ echo a >> a
   $ ln -s missing linka
   $ hg add linka
   $ hg falabala -r 0 --traceback
   diffing testsymlinks.07f494440405 testsymlinks
   [1]
   $ cd ..
 
 #endif