git-blame --incremental

git-blame --incremental

This adds --incremental option to help GUI porcelains to show
the result from git-blame incrementally.  The output gives the
origin information in the same format as the porcelain format.
The first line has commit object name, the line number of the
first line in the group in the original file, the line number of
that file in the final image, and number of lines in the group.
Then subsequent lines show the metainformation for the commit
when the commit is shown for the first time, except the filename
information is always shown (we cannot even make it conditional
to -C option as blame always follows the renaming of the file
wholesale).

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>