title: mergetool from .gitconfig being ignored?
body: <p><code>git config --global mergetool.bc3 "\"c:/program files (x86)/beyond compare 3/bcomp.exe\" \"$LOCAL\" \"$REMOTE\" \"$BASE\" \"$MERGED\""</code></p>
  
  <p><code>git mergetool</code></p>
  
  <p><code>/usr/lib/git-core/git-mergetool--lib: line 116: bcompare: command not found</code></p>
  
  <p>This is extremely odd, because both <code>./.git/config</code> and <code>~/.gitconfig</code> look correct. Neither lists an entry for <code>bcompare</code>. Can git read or store configuration from anywhere other than <code>.git/config</code> or <code>~/.gitconfig</code>?</p>