revision.c: --full-history fix.

With history simplification, we still show merges that are required
to make the history _complete_, i.e. say that you had:

	  a
	  |
	  b
	 / \
	c   d
	|   |

and neither "a" nor "b" actually changed the file, but both "c" and "d"
did: in this case we have to leave "b" around just because otherwise there
would be no way to show the _relationship_, even if "b" itself doesn't
actually change the tree in any way what-so-ever.

It would make sense to make that further simplification if the
"--parents" flag wasn't present.  In that case the user is
literally asking for a list of commits and is not interested in
the relationship between them.

This patch also fixes a real bug.  Without this patch, the
"--parents --full-history" combination (which you'd get if you
do something like

	gitk --full-history Makefile

or similar) will actually _drop_ merges where all children are identical.
That's wrong in the --full-history case, because it means that the graph
ends up missing lots of entries.

In the process, this also should make

	git-rev-list --full-history Makefile

give just the _true_ list of all commits that changed Makefile (and
properly ignore merges that were identical in one parent), because now
we're not asking for "--parent", so we don't need the unnecessary merge
commits to keep the history together.

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

diff --git a/revision.c b/revision.c
index b963f2adfd92050310f7327e1ee10e21d5996a7c..1cf6276ad8fdfa957bd7b3734494467c40e74962 100644 (file)
--- a/revision.c
+++ b/revision.c
@@ -280,7 +280,7 @@ int rev_same_tree_as_empty(struct rev_info *revs, struct tree *t1)
 static void try_to_simplify_commit(struct rev_info *revs, struct commit *commit)
 {
        struct commit_list **pp, *parent;
-       int tree_changed = 0;
+       int tree_changed = 0, tree_same = 0;
 
        if (!commit->tree)
                return;
@@ -298,6 +298,7 @@ static void try_to_simplify_commit(struct rev_info *revs, struct commit *commit)
                parse_commit(p);
                switch (rev_compare_tree(revs, p->tree, commit->tree)) {
                case REV_TREE_SAME:
+                       tree_same = 1;
                        if (!revs->simplify_history || (p->object.flags & UNINTERESTING)) {
                                /* Even if a merge with an uninteresting
                                 * side branch brought the entire change
@@ -334,7 +335,7 @@ static void try_to_simplify_commit(struct rev_info *revs, struct commit *commit)
                }
                die("bad tree compare for commit %s", sha1_to_hex(commit->object.sha1));
        }
-       if (tree_changed)
+       if (tree_changed && !tree_same)
                commit->object.flags |= TREECHANGE;
 }
 
@@ -896,6 +897,8 @@ static int rewrite_one(struct rev_info *revs, struct commit **pp)
                struct commit *p = *pp;
                if (!revs->limited)
                        add_parents_to_list(revs, p, &revs->commits);
+               if (p->parents && p->parents->next)
+                       return 0;
                if (p->object.flags & (TREECHANGE | UNINTERESTING))
                        return 0;
                if (!p->parents)
@@ -988,8 +991,15 @@ struct commit *get_revision(struct rev_info *revs)
                    commit->parents && commit->parents->next)
                        continue;
                if (revs->prune_fn && revs->dense) {
-                       if (!(commit->object.flags & TREECHANGE))
-                               continue;
+                       /* Commit without changes? */
+                       if (!(commit->object.flags & TREECHANGE)) {
+                               /* drop merges unless we want parenthood */
+                               if (!revs->parents)
+                                       continue;
+                               /* non-merge - always ignore it */
+                               if (commit->parents && !commit->parents->next)
+                                       continue;
+                       }
                        if (revs->parents)
                                rewrite_parents(revs, commit);
                }