Can TortoiseMerge be used as a difftool with Windows Git Bash?

So that filenames with spaces are handled correctly, you should change the last line of @melbourn's answer to

cmd = \""c:/Program Files/TortoiseGIT/bin/TortoiseGitMerge.exe"\" -base "$BASE" -theirs "$REMOTE" -mine "$LOCAL" -merged "$MERGED"

The following settings work fine for me. However, I am using TortoiseGit not TortoiseSVN. Notice the difference in the parameters for diff.

[diff]
  tool = tortoisediff
[difftool]
  prompt = false
[merge]
  tool = tortoisemerge
[mergetool]
  prompt = false
  keepBackup = false
[difftool "tortoisediff"]
  cmd = \""c:/Program Files/TortoiseGIT/bin/TortoiseGitMerge.exe"\" -mine "$REMOTE" -base "$LOCAL"
[mergetool "tortoisemerge"]
  cmd = \""c:/Program Files/TortoiseGIT/bin/TortoiseGitMerge.exe"\" -base "$BASE" -theirs "$REMOTE" -mine "$LOCAL" -merged "$MERGED"