git wrapper: DWIM mistyped commands

This patch introduces a modified Damerau-Levenshtein algorithm into
Git's code base, and uses it with the following penalties to show some
similar commands when an unknown command was encountered:

	swap = 0, insertion = 1, substitution = 2, deletion = 4

A typical output would now look like this:

	$ git sm
	git: 'sm' is not a git-command. See 'git --help'.

	Did you mean one of these?
		am
		rm

The cut-off is at similarity rating 6, which was empirically determined
to give sensible results.

As a convenience, if there is only one candidate, Git continues under
the assumption that the user mistyped it.  Example:

	$ git reabse
	WARNING: You called a Git program named 'reabse', which does
	not exist.
	Continuing under the assumption that you meant 'rebase'
	[...]

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Alex Riesen <raa.lkml@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 3 insertions, 1 deletions

diff --git a/git.c b/git.c
index 37b1d76a08..54c5bfa69b 100644
--- a/git.c
+++ b/git.c
@@ -499,7 +499,9 @@ int main(int argc, const char **argv)
 				cmd, argv[0]);
 			exit(1);
 		}
-		help_unknown_cmd(cmd);
+		argv[0] = help_unknown_cmd(cmd);
+		handle_internal_command(argc, argv);
+		execv_dashed_external(argv);
 	}
 
 	fprintf(stderr, "Failed to run command '%s': %s\n",