Merge branch 'kd/rev-list-bisect-first-parent'

"git rev-list --bisect --first-parent" does not work (yet) and can
even cause SEGV; forbid it.  "git log --bisect --first-parent"
would not be useful until "git bisect --first-parent" materializes,
so it is also forbidden for now.

* kd/rev-list-bisect-first-parent:
  rev-list: refuse --first-parent combined with --bisect

Author: gitster

Documentation/rev-list-options.txt

@@ -123,7 +123,8 @@ parents) and `--max-parents=-1` (negative numbers denote no upper limit).
 	because merges into a topic branch tend to be only about
 	adjusting to updated upstream from time to time, and
 	this option allows you to ignore the individual commits
-	brought in to your history by such a merge.
+	brought in to your history by such a merge. Cannot be
+	combined with --bisect.
 
 --not::
 	Reverses the meaning of the '{caret}' prefix (or lack thereof)
@@ -185,7 +186,7 @@ ifndef::git-rev-list[]
 	Pretend as if the bad bisection ref `refs/bisect/bad`
 	was listed and as if it was followed by `--not` and the good
 	bisection refs `refs/bisect/good-*` on the command
-	line.
+	line. Cannot be combined with --first-parent.
 endif::git-rev-list[]
 
 --stdin::
@@ -566,7 +567,7 @@ outputs 'midpoint', the output of the two commands
 would be of roughly the same length.  Finding the change which
 introduces a regression is thus reduced to a binary search: repeatedly
 generate and test new 'midpoint's until the commit chain is of length
-one.
+one. Cannot be combined with --first-parent.
 
 --bisect-vars::
 	This calculates the same as `--bisect`, except that refs in

revision.c

@@ -2342,6 +2342,9 @@ int setup_revisions(int argc, const char **argv, struct rev_info *revs, struct s
 	if (!revs->reflog_info && revs->grep_filter.use_reflog_filter)
 		die("cannot use --grep-reflog without --walk-reflogs");
 
+	if (revs->first_parent_only && revs->bisect)
+		die(_("--first-parent is incompatible with --bisect"));
+
 	return left;
 }
 

t/t6000-rev-list-misc.sh

@@ -96,4 +96,8 @@ test_expect_success 'rev-list can show index objects' '
 	test_cmp expect actual
 '
 
+test_expect_success '--bisect and --first-parent can not be combined' '
+	test_must_fail git rev-list --bisect --first-parent HEAD
+'
+
 test_done