MSysGit mergetool broken after 1.7.7

I've been using Git on Windows (MSysGit) happily with BeyondCompare 3 for quite a while. Mostly I use BC3 to view changes. Occasionally I use it to merge conflicts. I don't merge very often, thanks to Git's powerful merging capability. It has worked fine. Recently I upgraded to version 1.7.10-preview20120409, and suddenly the git's merge command always fail with below error messages:

Merging:
my/path/filename.cs

Normal merge conflict for 'my/path/filename.cs':
  {local}: modified file
  {remote}: modified file
Hit return to start merge resolution tool (BC3):
git_path/libexec/git-core/mergetools/BC3: line 9: bcompare: command not found
my/path/filename.cs seems unchanged.
Was the merge successful? [y/n] n

Where is this line 9? It turns out that it seems MSysGit (or Git?) has put all merge tools to a folder named "git_path/libexec/git-core/mergetools/". In my installation, I can already find quite a bunch of tools:

araxis
bc3
defaults
deltawalker
diffuse
ecmerge
emerge
kdiff3
kompare
meld
opendiff
p4merge
tkdiff
tortoisemerge
vim
xxdiff

and they are actually bash scripts. For example, the bc3 file is like below:

diff_cmd () {
 "$merge_tool_path" "$LOCAL" "$REMOTE"
}

merge_cmd () {
 touch "$BACKUP"
 if $base_present
 then
  "$merge_tool_path" "$LOCAL" "$REMOTE" "$BASE" \
   -mergeoutput="$MERGED"
 else
  "$merge_tool_path" "$LOCAL" "$REMOTE" \
   -mergeoutput="$MERGED"
 fi
 check_unchanged
}

translate_merge_tool_path() {
 if type bcomp >/dev/null 2>/dev/null
 then
  echo bcomp
 else
  echo bcompare
 fi
}

and there is really is a line 9! Of course directly modify the file will do the trick. But I guess there are better ways. After testing around, trying to override the merge_tool_path environment variable, I found it's easier if I just put BC3's folder to path, and nothing else need to be changed!