Teach revision walking machinery to walk multiple times sequencially

Previously it was not possible to iterate revisions twice using the
revision walking api. We add a reset_revision_walk() which clears the
used flags. This allows us to do multiple sequencial revision walks.

We add the appropriate calls to the existing submodule machinery doing
revision walks. This is done to avoid surprises if future code wants to
call these functions more than once during the processes lifetime.

Signed-off-by: Heiko Voigt <hvoigt@hvoigt.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

10 files changed, 127 insertions, 0 deletions

diff --git a/.gitignore b/.gitignore
index 87fcc5f6f..382481cd4 100644
--- a/.gitignore
+++ b/.gitignore
@@ -183,6 +183,7 @@
 /test-mktemp
 /test-parse-options
 /test-path-utils
+/test-revision-walking
 /test-run-command
 /test-sha1
 /test-sigchain
diff --git a/Documentation/technical/api-revision-walking.txt b/Documentation/technical/api-revision-walking.txt
index 996da0503..b7d0d9a8a 100644
--- a/Documentation/technical/api-revision-walking.txt
+++ b/Documentation/technical/api-revision-walking.txt
@@ -56,6 +56,11 @@ function.
 	returning a `struct commit *` each time you call it. The end of the
 	revision list is indicated by returning a NULL pointer.
 
+`reset_revision_walk`::
+
+	Reset the flags used by the revision walking api. You can use
+	this to do multiple sequencial revision walks.
+
 Data structures
 ---------------
 
diff --git a/Makefile b/Makefile
index 2bce23e5e..681134a75 100644
--- a/Makefile
+++ b/Makefile
@@ -479,6 +479,7 @@ TEST_PROGRAMS_NEED_X += test-match-trees
 TEST_PROGRAMS_NEED_X += test-mktemp
 TEST_PROGRAMS_NEED_X += test-parse-options
 TEST_PROGRAMS_NEED_X += test-path-utils
+TEST_PROGRAMS_NEED_X += test-revision-walking
 TEST_PROGRAMS_NEED_X += test-run-command
 TEST_PROGRAMS_NEED_X += test-sha1
 TEST_PROGRAMS_NEED_X += test-sigchain
diff --git a/object.c b/object.c
index 6b06297a5..f84e80a95 100644
--- a/object.c
+++ b/object.c
@@ -275,3 +275,14 @@ void object_array_remove_duplicates(struct object_array *array)
 		array->nr = dst;
 	}
 }
+
+void clear_object_flags(unsigned flags)
+{
+	int i;
+
+	for (i=0; i < obj_hash_size; i++) {
+		struct object *obj = obj_hash[i];
+		if (obj)
+			obj->flags &= ~flags;
+	}
+}
diff --git a/object.h b/object.h
index b6618d92b..6a97b6ba1 100644
--- a/object.h
+++ b/object.h
@@ -76,4 +76,6 @@ void add_object_array(struct object *obj, const char *name, struct object_array
 void add_object_array_with_mode(struct object *obj, const char *name, struct object_array *array, unsigned mode);
 void object_array_remove_duplicates(struct object_array *);
 
+void clear_object_flags(unsigned flags);
+
 #endif /* OBJECT_H */
diff --git a/revision.c b/revision.c
index c97d83448..4fbc14b6b 100644
--- a/revision.c
+++ b/revision.c
@@ -2061,6 +2061,11 @@ static void set_children(struct rev_info *revs)
 	}
 }
 
+void reset_revision_walk(void)
+{
+	clear_object_flags(SEEN | ADDED | SHOWN);
+}
+
 int prepare_revision_walk(struct rev_info *revs)
 {
 	int nr = revs->pending.nr;
diff --git a/revision.h b/revision.h
index b8e922395..eb87fd1e2 100644
--- a/revision.h
+++ b/revision.h
@@ -192,6 +192,7 @@ extern void parse_revision_opt(struct rev_info *revs, struct parse_opt_ctx_t *ct
 				 const char * const usagestr[]);
 extern int handle_revision_arg(const char *arg, struct rev_info *revs,int flags,int cant_be_filename);
 
+extern void reset_revision_walk(void);
 extern int prepare_revision_walk(struct rev_info *revs);
 extern struct commit *get_revision(struct rev_info *revs);
 extern char *get_revision_mark(const struct rev_info *revs, const struct commit *commit);
diff --git a/submodule.c b/submodule.c
index 9a2806067..645ff5db0 100644
--- a/submodule.c
+++ b/submodule.c
@@ -404,6 +404,7 @@ int check_submodule_needs_pushing(unsigned char new_sha1[20], const char *remote
 	while ((commit = get_revision(&rev)) && !needs_pushing)
 		commit_need_pushing(commit, &needs_pushing);
 
+	reset_revision_walk();
 	free(sha1_copy);
 	strbuf_release(&remotes_arg);
 
@@ -741,6 +742,7 @@ static int find_first_merges(struct object_array *result, const char *path,
 		if (in_merge_bases(b, &commit, 1))
 			add_object_array(o, NULL, &merges);
 	}
+	reset_revision_walk();
 
 	/* Now we've got all merges that contain a and b. Prune all
 	 * merges that contain another found merge and save them in
diff --git a/t/t0062-revision-walking.sh b/t/t0062-revision-walking.sh
new file mode 100755
index 000000000..3d98eb847
--- /dev/null
+++ b/t/t0062-revision-walking.sh
@@ -0,0 +1,33 @@
+#!/bin/sh
+#
+# Copyright (c) 2012 Heiko Voigt
+#
+
+test_description='Test revision walking api'
+
+. ./test-lib.sh
+
+cat >run_twice_expected <<-EOF
+1st
+ > add b
+ > add a
+2nd
+ > add b
+ > add a
+EOF
+
+test_expect_success 'setup' '
+	echo a > a &&
+	git add a &&
+	git commit -m "add a" &&
+	echo b > b &&
+	git add b &&
+	git commit -m "add b"
+'
+
+test_expect_success 'revision walking can be done twice' '
+	test-revision-walking run-twice > run_twice_actual
+	test_cmp run_twice_expected run_twice_actual
+'
+
+test_done
diff --git a/test-revision-walking.c b/test-revision-walking.c
new file mode 100644
index 000000000..3ade02c72
--- /dev/null
+++ b/test-revision-walking.c
@@ -0,0 +1,66 @@
+/*
+ * test-revision-walking.c: test revision walking API.
+ *
+ * (C) 2012 Heiko Voigt <hvoigt@hvoigt.net>
+ *
+ * This code is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include "cache.h"
+#include "commit.h"
+#include "diff.h"
+#include "revision.h"
+
+static void print_commit(struct commit *commit)
+{
+	struct strbuf sb = STRBUF_INIT;
+	struct pretty_print_context ctx = {0};
+	ctx.date_mode = DATE_NORMAL;
+	format_commit_message(commit, " %m %s", &sb, &ctx);
+	printf("%s\n", sb.buf);
+	strbuf_release(&sb);
+}
+
+static int run_revision_walk(void)
+{
+	struct rev_info rev;
+	struct commit *commit;
+	const char *argv[] = {NULL, "--all", NULL};
+	int argc = ARRAY_SIZE(argv) - 1;
+	int got_revision = 0;
+
+	init_revisions(&rev, NULL);
+	setup_revisions(argc, argv, &rev, NULL);
+	if (prepare_revision_walk(&rev))
+		die("revision walk setup failed");
+
+	while ((commit = get_revision(&rev)) != NULL) {
+		print_commit(commit);
+		got_revision = 1;
+	}
+
+	reset_revision_walk();
+	return got_revision;
+}
+
+int main(int argc, char **argv)
+{
+	if (argc < 2)
+		return 1;
+
+	if (!strcmp(argv[1], "run-twice")) {
+		printf("1st\n");
+		if (!run_revision_walk())
+			return 1;
+		printf("2nd\n");
+		if (!run_revision_walk())
+			return 1;
+
+		return 0;
+	}
+
+	fprintf(stderr, "check usage\n");
+	return 1;
+}