Merge branch 'nd/log-show-linear-break'

Attempts to show where a single-strand-of-pearls break in "git log"
output.

* nd/log-show-linear-break:
  log: add --show-linear-break to help see non-linear history
  object.h: centralize object flag allocation

14 files changed, 89 insertions, 11 deletions

diff --git a/Documentation/rev-list-options.txt b/Documentation/rev-list-options.txt
index 9a3da3646e..b8139610b9 100644
--- a/Documentation/rev-list-options.txt
+++ b/Documentation/rev-list-options.txt
@@ -758,6 +758,13 @@ This enables parent rewriting, see 'History Simplification' below.
 This implies the `--topo-order` option by default, but the
 `--date-order` option may also be specified.
 
+--show-linear-break[=<barrier>]::
+	When --graph is not used, all history branches are flattened
+	which can make it hard to see that the two consecutive commits
+	do not belong to a linear branch. This option puts a barrier
+	in between them in that case. If `<barrier>` is specified, it
+	is the string that will be shown instead of the default one.
+
 ifdef::git-rev-list[]
 --count::
 	Print a number stating how many commits would have been
diff --git a/bisect.c b/bisect.c
index 8448d27877..d6e851d783 100644
--- a/bisect.c
+++ b/bisect.c
@@ -21,8 +21,7 @@ static const char *argv_checkout[] = {"checkout", "-q", NULL, "--", NULL};
 static const char *argv_show_branch[] = {"show-branch", NULL, NULL};
 static const char *argv_update_ref[] = {"update-ref", "--no-deref", "BISECT_HEAD", NULL, NULL};
 
-/* bits #0-15 in revision.h */
-
+/* Remember to update object flag allocation in object.h */
 #define COUNTED		(1u<<16)
 
 /*
diff --git a/builtin/blame.c b/builtin/blame.c
index e5b5d71bad..88cb799727 100644
--- a/builtin/blame.c
+++ b/builtin/blame.c
@@ -74,7 +74,7 @@ static unsigned blame_copy_score;
 #define BLAME_DEFAULT_MOVE_SCORE	20
 #define BLAME_DEFAULT_COPY_SCORE	40
 
-/* bits #0..7 in revision.h, #8..11 used for merge_bases() in commit.c */
+/* Remember to update object flag allocation in object.h */
 #define METAINFO_SHOWN		(1u<<12)
 #define MORE_THAN_ONE_PATH	(1u<<13)
 
diff --git a/bundle.c b/bundle.c
index a85e0e4532..1222952075 100644
--- a/bundle.c
+++ b/bundle.c
@@ -120,6 +120,7 @@ static int list_refs(struct ref_list *r, int argc, const char **argv)
 	return 0;
 }
 
+/* Remember to update object flag allocation in object.h */
 #define PREREQ_MARK (1u<<16)
 
 int verify_bundle(struct bundle_header *header, int verbose)
diff --git a/commit.c b/commit.c
index 0f28902bc3..f4793316a2 100644
--- a/commit.c
+++ b/commit.c
@@ -721,7 +721,7 @@ void sort_in_topological_order(struct commit_list **list, enum rev_sort_order so
 
 /* merge-base stuff */
 
-/* bits #0..15 in revision.h */
+/* Remember to update object flag allocation in object.h */
 #define PARENT1		(1u<<16)
 #define PARENT2		(1u<<17)
 #define STALE		(1u<<18)
diff --git a/fetch-pack.c b/fetch-pack.c
index 90d47da8a9..eeee2bb7e0 100644
--- a/fetch-pack.c
+++ b/fetch-pack.c
@@ -26,6 +26,7 @@ static int agent_supported;
 static struct lock_file shallow_lock;
 static const char *alternate_shallow_file;
 
+/* Remember to update object flag allocation in object.h */
 #define COMPLETE	(1U << 0)
 #define COMMON		(1U << 1)
 #define COMMON_REF	(1U << 2)
diff --git a/http-push.c b/http-push.c
index d4b40c9c60..f2c56c8454 100644
--- a/http-push.c
+++ b/http-push.c
@@ -64,8 +64,7 @@ enum XML_Status {
 #define LOCK_TIME 600
 #define LOCK_REFRESH 30
 
-/* bits #0-15 in revision.h */
-
+/* Remember to update object flag allocation in object.h */
 #define LOCAL    (1u<<16)
 #define REMOTE   (1u<<17)
 #define FETCHING (1u<<18)
diff --git a/log-tree.c b/log-tree.c
index 5ce217d5eb..cf2f86c866 100644
--- a/log-tree.c
+++ b/log-tree.c
@@ -805,12 +805,16 @@ int log_tree_commit(struct rev_info *opt, struct commit *commit)
 	if (opt->line_level_traverse)
 		return line_log_print(opt, commit);
 
+	if (opt->track_linear && !opt->linear && !opt->reverse_output_stage)
+		printf("\n%s\n", opt->break_bar);
 	shown = log_tree_diff(opt, commit, &log);
 	if (!shown && opt->loginfo && opt->always_show_header) {
 		log.parent = NULL;
 		show_log(opt);
 		shown = 1;
 	}
+	if (opt->track_linear && !opt->linear && opt->reverse_output_stage)
+		printf("\n%s\n", opt->break_bar);
 	opt->loginfo = NULL;
 	maybe_flush_or_die(stdout, "stdout");
 	return shown;
diff --git a/object.h b/object.h
index 732bf4d7e7..6e12f2c7f4 100644
--- a/object.h
+++ b/object.h
@@ -26,6 +26,19 @@ struct object_array {
 #define OBJECT_ARRAY_INIT { 0, 0, NULL }
 
 #define TYPE_BITS   3
+/*
+ * object flag allocation:
+ * revision.h:      0---------10                                26
+ * fetch-pack.c:    0---4
+ * walker.c:        0-2
+ * upload-pack.c:               11----------------19
+ * builtin/blame.c:               12-13
+ * bisect.c:                               16
+ * bundle.c:                               16
+ * http-push.c:                            16-----19
+ * commit.c:                               16-----19
+ * sha1_name.c:                                     20
+ */
 #define FLAG_BITS  27
 
 /*
diff --git a/revision.c b/revision.c
index 85085501f6..794a8835c0 100644
--- a/revision.c
+++ b/revision.c
@@ -1837,6 +1837,14 @@ static int handle_revision_opt(struct rev_info *revs, int argc, const char **arg
 		revs->notes_opt.use_default_notes = 1;
 	} else if (!strcmp(arg, "--show-signature")) {
 		revs->show_signature = 1;
+	} else if (!strcmp(arg, "--show-linear-break") ||
+		   starts_with(arg, "--show-linear-break=")) {
+		if (starts_with(arg, "--show-linear-break="))
+			revs->break_bar = xstrdup(arg + 20);
+		else
+			revs->break_bar = "                    ..........";
+		revs->track_linear = 1;
+		revs->track_first_time = 1;
 	} else if (starts_with(arg, "--show-notes=") ||
 		   starts_with(arg, "--notes=")) {
 		struct strbuf buf = STRBUF_INIT;
@@ -1960,6 +1968,8 @@ static int handle_revision_opt(struct rev_info *revs, int argc, const char **arg
 			unkv[(*unkc)++] = arg;
 		return opts;
 	}
+	if (revs->graph && revs->track_linear)
+		die("--show-linear-break and --graph are incompatible");
 
 	return 1;
 }
@@ -2902,6 +2912,27 @@ enum commit_action simplify_commit(struct rev_info *revs, struct commit *commit)
 	return action;
 }
 
+static void track_linear(struct rev_info *revs, struct commit *commit)
+{
+	if (revs->track_first_time) {
+		revs->linear = 1;
+		revs->track_first_time = 0;
+	} else {
+		struct commit_list *p;
+		for (p = revs->previous_parents; p; p = p->next)
+			if (p->item == NULL || /* first commit */
+			    !hashcmp(p->item->object.sha1, commit->object.sha1))
+				break;
+		revs->linear = p != NULL;
+	}
+	if (revs->reverse) {
+		if (revs->linear)
+			commit->object.flags |= TRACK_LINEAR;
+	}
+	free_commit_list(revs->previous_parents);
+	revs->previous_parents = copy_commit_list(commit->parents);
+}
+
 static struct commit *get_revision_1(struct rev_info *revs)
 {
 	if (!revs->commits)
@@ -2941,6 +2972,8 @@ static struct commit *get_revision_1(struct rev_info *revs)
 			die("Failed to simplify parents of commit %s",
 			    sha1_to_hex(commit->object.sha1));
 		default:
+			if (revs->track_linear)
+				track_linear(revs, commit);
 			return commit;
 		}
 	} while (revs->commits);
@@ -3107,14 +3140,23 @@ struct commit *get_revision(struct rev_info *revs)
 		revs->reverse_output_stage = 1;
 	}
 
-	if (revs->reverse_output_stage)
-		return pop_commit(&revs->commits);
+	if (revs->reverse_output_stage) {
+		c = pop_commit(&revs->commits);
+		if (revs->track_linear)
+			revs->linear = !!(c && c->object.flags & TRACK_LINEAR);
+		return c;
+	}
 
 	c = get_revision_internal(revs);
 	if (c && revs->graph)
 		graph_update(revs->graph, c);
-	if (!c)
+	if (!c) {
 		free_saved_parents(revs);
+		if (revs->previous_parents) {
+			free_commit_list(revs->previous_parents);
+			revs->previous_parents = NULL;
+		}
+	}
 	return c;
 }
 
diff --git a/revision.h b/revision.h
index 1eb94c1548..d9907dd460 100644
--- a/revision.h
+++ b/revision.h
@@ -7,6 +7,7 @@
 #include "commit.h"
 #include "diff.h"
 
+/* Remember to update object flag allocation in object.h */
 #define SEEN		(1u<<0)
 #define UNINTERESTING   (1u<<1)
 #define TREESAME	(1u<<2)
@@ -18,7 +19,8 @@
 #define SYMMETRIC_LEFT	(1u<<8)
 #define PATCHSAME	(1u<<9)
 #define BOTTOM		(1u<<10)
-#define ALL_REV_FLAGS	((1u<<11)-1)
+#define TRACK_LINEAR	(1u<<26)
+#define ALL_REV_FLAGS	(((1u<<11)-1) | TRACK_LINEAR)
 
 #define DECORATE_SHORT_REFS	1
 #define DECORATE_FULL_REFS	2
@@ -137,6 +139,10 @@ struct rev_info {
 			preserve_subject:1;
 	unsigned int	disable_stdin:1;
 	unsigned int	leak_pending:1;
+	/* --show-linear-break */
+	unsigned int	track_linear:1,
+			track_first_time:1,
+			linear:1;
 
 	enum date_mode date_mode;
 
@@ -197,6 +203,9 @@ struct rev_info {
 
 	/* copies of the parent lists, for --full-diff display */
 	struct saved_parents *saved_parents_slab;
+
+	struct commit_list *previous_parents;
+	const char *break_bar;
 };
 
 extern int ref_excluded(struct string_list *, const char *path);
diff --git a/sha1_name.c b/sha1_name.c
index 6fca8692d2..2b6322fad0 100644
--- a/sha1_name.c
+++ b/sha1_name.c
@@ -819,6 +819,8 @@ static int get_sha1_1(const char *name, int len, unsigned char *sha1, unsigned l
  * For future extension, ':/!' is reserved. If you want to match a message
  * beginning with a '!', you have to repeat the exclamation mark.
  */
+
+/* Remember to update object flag allocation in object.h */
 #define ONELINE_SEEN (1u<<20)
 
 static int handle_one_ref(const char *path,
diff --git a/upload-pack.c b/upload-pack.c
index 286a9ed3ea..01de944a0a 100644
--- a/upload-pack.c
+++ b/upload-pack.c
@@ -17,7 +17,7 @@
 
 static const char upload_pack_usage[] = "git upload-pack [--strict] [--timeout=<n>] <dir>";
 
-/* bits #0..7 in revision.h, #8..10 in commit.c */
+/* Remember to update object flag allocation in object.h */
 #define THEY_HAVE	(1u << 11)
 #define OUR_REF		(1u << 12)
 #define WANTED		(1u << 13)
diff --git a/walker.c b/walker.c
index 633596e06f..1dd86b8f33 100644
--- a/walker.c
+++ b/walker.c
@@ -60,6 +60,7 @@ static int process_tree(struct walker *walker, struct tree *tree)
 	return 0;
 }
 
+/* Remember to update object flag allocation in object.h */
 #define COMPLETE	(1U << 0)
 #define SEEN		(1U << 1)
 #define TO_SCAN		(1U << 2)