[PATCH 1/2] Clean up reflog unreachability pruning decision

[Linus Torvalds <torvalds@linux-foundation.org>]

From: Linus Torvalds <torvalds@linux-foundation.org>
Date: Tue, 31 Mar 2009 09:45:22 -0700

This clarifies the pruning rules for unreachable commits by having a 
separate helpder function for the unreachability decision.

It's preparation for actual bigger changes to come to speed up the
decision when the reachability calculations become a bottleneck.

In the process it also _does_ change behavior, although in a way that I 
think is much saner than the old behavior (which was in my opinion not 
designed, just a result of how the tests were written). It now will prune 
reflog entries that are older than that 'prune_unreacable' time _and_ that 
have commit references that can't be even looked up.

Of course, "--stale-fix" also does that, and does it regardless of the age 
of the reflog entry is, but I really think this is the right thing to do. 
If we can't even look it up, we should consider it to be unreachable.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
 builtin-reflog.c |   32 ++++++++++++++++++++++++++------
 1 files changed, 26 insertions(+), 6 deletions(-)

Note the behavioural change. I think it's sane and "ObviouslyCorrect(tm)", 
but maybe somebody disagrees.

diff --git a/builtin-reflog.c b/builtin-reflog.c
index d95f515..0355ce6 100644
--- a/builtin-reflog.c
+++ b/builtin-reflog.c
@@ -209,6 +209,31 @@ static int keep_entry(struct commit **it, unsigned char *sha1)
 	return 1;
 }
 
+static int unreachable(struct expire_reflog_cb *cb, struct commit *commit, unsigned char *sha1)
+{
+	/*
+	 * We may or may not have the commit yet - if not, look it
+	 * up using the supplied sha1.
+	 */
+	if (!commit) {
+		if (is_null_sha1(sha1))
+			return 0;
+
+		commit = lookup_commit_reference_gently(sha1, 1);
+
+		/* We can't even look it up - consider it unreachable */
+		if (!commit)
+			return 1;
+	}
+
+	/* Reachable from the current reflog top? Don't prune */
+	if (in_merge_bases(commit, &cb->ref_commit, 1))
+		return 0;
+
+	/* We can't reach it - prune it. */
+	return 1;
+}
+
 static int expire_reflog_ent(unsigned char *osha1, unsigned char *nsha1,
 		const char *email, unsigned long timestamp, int tz,
 		const char *message, void *cb_data)
@@ -230,12 +255,7 @@ static int expire_reflog_ent(unsigned char *osha1, unsigned char *nsha1,
 	if (timestamp < cb->cmd->expire_unreachable) {
 		if (!cb->ref_commit)
 			goto prune;
-		if (!old && !is_null_sha1(osha1))
-			old = lookup_commit_reference_gently(osha1, 1);
-		if (!new && !is_null_sha1(nsha1))
-			new = lookup_commit_reference_gently(nsha1, 1);
-		if ((old && !in_merge_bases(old, &cb->ref_commit, 1)) ||
-		    (new && !in_merge_bases(new, &cb->ref_commit, 1)))
+		if (unreachable(cb, old, osha1) || unreachable(cb, new, nsha1))
 			goto prune;
 	}
 
-- 
1.6.2.1.404.gb0085.dirty