convert: config option for git rename limit

By default, Git applies rename and copy detection to 400 files. The
diff.renamelimit config option and -l argument to diff commands can
override this.

As part of converting some repositories in the wild, I was hitting
the default limit. Unfortunately, the warnings that Git prints in this
scenario are swallowed because the process running functionality in
common.py redirects stderr to /dev/null by default. This seems like
a bug, but a bug for another day.

This commit establishes a config option to send the rename limit
through to `git diff-tree`. The added tests demonstrate a too-low
rename limit doesn't result in copy metadata being recorded.

hgext/convert/__init__.py

@@ -320,6 +320,13 @@ def convert(ui, src, dest=None, revmapfile=None, **opts):
         is very expensive for large projects, and is only effective when
         ``convert.git.similarity`` is greater than 0. The default is False.
 
+    :convert.git.renamelimit: perform rename and copy detection up to this
+        many changed files in a commit. Increasing this will make rename
+        and copy detection more accurate but will significantly slow down
+        computation on large projects. The option is only relevant if
+        ``convert.git.similarity`` is greater than 0. The default is
+        ``400``.
+
     :convert.git.remoteprefix: remote refs are converted as bookmarks with
         ``convert.git.remoteprefix`` as a prefix followed by a /. The default
         is 'remote'.

hgext/convert/git.py

@@ -78,6 +78,10 @@ class convert_git(common.converter_source, common.commandline):
                                              False)
             if findcopiesharder:
                 self.simopt.append('--find-copies-harder')
+
+            renamelimit = ui.configint('convert', 'git.renamelimit',
+                                       default=400)
+            self.simopt.append('-l%d' % renamelimit)
         else:
             self.simopt = []
 

tests/test-convert-git.t

@@ -374,6 +374,31 @@ source, the copy source took the contents of the copy dest)
   A bar-copied2
     bar
 
+renamelimit config option works
+
+  $ cd git-repo2
+  $ cp bar bar-copy0
+  $ echo 0 >> bar-copy0
+  $ cp bar bar-copy1
+  $ echo 1 >> bar-copy1
+  $ git add bar-copy0 bar-copy1
+  $ commit -a -m 'copy bar 2 times'
+  $ cd ..
+
+  $ hg -q convert --config convert.git.renamelimit=1 \
+  > --config convert.git.findcopiesharder=true --datesort git-repo2 fullrepo2
+  $ hg -R fullrepo2 status -C --change master
+  A bar-copy0
+  A bar-copy1
+
+  $ hg -q convert --config convert.git.renamelimit=100 \
+  > --config convert.git.findcopiesharder=true --datesort git-repo2 fullrepo3
+  $ hg -R fullrepo3 status -C --change master
+  A bar-copy0
+    bar
+  A bar-copy1
+    bar
+
 test binary conversion (issue1359)
 
   $ count=19

tests/test-convert.t

@@ -261,6 +261,13 @@
                     for large projects, and is only effective when
                     "convert.git.similarity" is greater than 0. The default is
                     False.
+      convert.git.renamelimit
+                    perform rename and copy detection up to this many changed
+                    files in a commit. Increasing this will make rename and copy
+                    detection more accurate but will significantly slow down
+                    computation on large projects. The option is only relevant
+                    if "convert.git.similarity" is greater than 0. The default
+                    is "400".
       convert.git.remoteprefix
                     remote refs are converted as bookmarks with
                     "convert.git.remoteprefix" as a prefix followed by a /. The