Fix "--abbrev=xyz" for revision listing

The revision argument parsing was happily parsing "--abbrev", but it 
didn't parse "--abbrev=<n>".

Which was hidden by the fact that the diff options _would_ parse 
--abbrev=<n>, so it would actually silently parse it, it just 
wouldn't use it for the same things that a plain "--abbrev" was 
used for.

Which seems a bit insane.

With this patch, if you do "git log --abbrev=10" it will abbreviate the 
merge parent commit ID's to ten hex characters, which was probably what 
you expected.

Signed-off-by: Linus Torvalds <torvalds@osdl.org>
---

diff --git a/revision.c b/revision.c
index 2294b16..42c077a 100644
--- a/revision.c
+++ b/revision.c

@@ -733,6 +733,14 @@ int setup_revisions(int argc, const char
 				revs->abbrev = DEFAULT_ABBREV;
 				continue;
 			}
+			if (!strncmp(arg, "--abbrev=", 9)) {
+				revs->abbrev = strtoul(arg + 9, NULL, 10);
+				if (revs->abbrev < MINIMUM_ABBREV)
+					revs->abbrev = MINIMUM_ABBREV;
+				else if (revs->abbrev > 40)
+					revs->abbrev = 40;
+				continue;
+			}
 			if (!strcmp(arg, "--abbrev-commit")) {
 				revs->abbrev_commit = 1;
 				continue;