Merge branch 'maint-1.5.1' into maint

* maint-1.5.1:
  Fix git-svn to handle svn not reporting the md5sum of a file, and test.
  More echo "$user_message" fixes.
  Add tests for the last two fixes.
  git-commit: use printf '%s\n' instead of echo on user-supplied strings
  git-am: use printf instead of echo on user-supplied strings
  Documentation: Add definition of "evil merge" to GIT Glossary
  Replace the last 'dircache's by 'index'
  Documentation: Clean up links in GIT Glossary

diff.c

@@ -1349,7 +1349,7 @@ void fill_filespec(struct diff_filespec *spec, const unsigned char *sha1,
 }
 
 /*
- * Given a name and sha1 pair, if the dircache tells us the file in
+ * Given a name and sha1 pair, if the index tells us the file in
  * the work tree has that object contents, return true, so that
  * prepare_temp_file() does not have to inflate and extract.
  */