Merge branch 'cc/bisect' (early part)

* 'cc/bisect' (early part):
  bisect: make "git bisect" use new "--next-all" bisect-helper function
  bisect: add "check_good_are_ancestors_of_bad" function
  bisect: implement the "check_merge_bases" function
  bisect: automatically sort sha1_array if needed when looking it up
  bisect: make skipped array functions more generic
  bisect: remove too much function nesting
  bisect: use new "struct argv_array" to prepare argv for "setup_revisions"
  bisect: store good revisions in a "sha1_array"
  bisect: implement "rev_argv_push" to fill an argv with revs
  bisect: use "sha1_array" to store skipped revisions
  am: simplify "sq" function by using "git rev-parse --sq-quote"
  bisect: use "git rev-parse --sq-quote" instead of a custom "sq" function
  rev-parse: add --sq-quote to shell quote arguments
  rev-list: remove stringed output flag from "show_bisect_vars"
  bisect--helper: remove "--next-vars" option as it is now useless
  bisect: use "git bisect--helper --next-exit" in "git-bisect.sh"
  bisect--helper: add "--next-exit" to output bisect results
  bisect: move common bisect functionality to "bisect_common"
  rev-list: refactor printing bisect vars
  rev-list: make "estimate_bisect_steps" non static

9 files changed, 494 insertions, 271 deletions

diff --git a/Documentation/git-rev-parse.txt b/Documentation/git-rev-parse.txt
index 52c353e674..4bbdd056da 100644
--- a/Documentation/git-rev-parse.txt
+++ b/Documentation/git-rev-parse.txt
@@ -30,6 +30,11 @@ OPTIONS
 	Only meaningful in `--parseopt` mode. Tells the option parser to echo
 	out the first `--` met instead of skipping it.
 
+--sq-quote::
+	Use 'git-rev-parse' in shell quoting mode (see SQ-QUOTE
+	section below). In contrast to the `--sq` option below, this
+	mode does only quoting. Nothing else is done to command input.
+
 --revs-only::
 	Do not output flags and parameters not meant for
 	'git-rev-list' command.
@@ -64,7 +69,8 @@ OPTIONS
 	properly quoted for consumption by shell.  Useful when
 	you expect your parameter to contain whitespaces and
 	newlines (e.g. when using pickaxe `-S` with
-	'git-diff-\*').
+	'git-diff-\*'). In contrast to the `--sq-quote` option,
+	the command input is still interpreted as usual.
 
 --not::
 	When showing object names, prefix them with '{caret}' and
@@ -406,6 +412,33 @@ C?        option C with an optional argument"
 eval `echo "$OPTS_SPEC" | git rev-parse --parseopt -- "$@" || echo exit $?`
 ------------
 
+SQ-QUOTE
+--------
+
+In `--sq-quote` mode, 'git-rev-parse' echoes on the standard output a
+single line suitable for `sh(1)` `eval`. This line is made by
+normalizing the arguments following `--sq-quote`. Nothing other than
+quoting the arguments is done.
+
+If you want command input to still be interpreted as usual by
+'git-rev-parse' before the output is shell quoted, see the `--sq`
+option.
+
+Example
+~~~~~~~
+
+------------
+$ cat >your-git-script.sh <<\EOF
+#!/bin/sh
+args=$(git rev-parse --sq-quote "$@")   # quote user-supplied arguments
+command="git frotz -n24 $args"          # and use it inside a handcrafted
+					# command line
+eval "$command"
+EOF
+
+$ sh your-git-script.sh "a b'c"
+------------
+
 EXAMPLES
 --------
 
diff --git a/Makefile b/Makefile
index 26d180cc54..3ef9230f77 100644
--- a/Makefile
+++ b/Makefile
@@ -1249,7 +1249,6 @@ $(patsubst %.sh,%,$(SCRIPT_SH)) : % : %.sh
 	$(QUIET_GEN)$(RM) $@ $@+ && \
 	sed -e '1s|#!.*/sh|#!$(SHELL_PATH_SQ)|' \
 	    -e 's|@SHELL_PATH@|$(SHELL_PATH_SQ)|' \
-	    -e 's|@@PERL@@|$(PERL_PATH_SQ)|g' \
 	    -e 's/@@GIT_VERSION@@/$(GIT_VERSION)/g' \
 	    -e 's/@@NO_CURL@@/$(NO_CURL)/g' \
 	    $@.sh >$@+ && \
diff --git a/bisect.c b/bisect.c
index 58f7e6f773..f57b62cddd 100644
--- a/bisect.c
+++ b/bisect.c
@@ -6,15 +6,30 @@
 #include "list-objects.h"
 #include "quote.h"
 #include "sha1-lookup.h"
+#include "run-command.h"
 #include "bisect.h"
 
-static unsigned char (*skipped_sha1)[20];
-static int skipped_sha1_nr;
-static int skipped_sha1_alloc;
+struct sha1_array {
+	unsigned char (*sha1)[20];
+	int sha1_nr;
+	int sha1_alloc;
+	int sorted;
+};
+
+static struct sha1_array good_revs;
+static struct sha1_array skipped_revs;
+
+static const unsigned char *current_bad_sha1;
+
+struct argv_array {
+	const char **argv;
+	int argv_nr;
+	int argv_alloc;
+};
 
-static const char **rev_argv;
-static int rev_argv_nr;
-static int rev_argv_alloc;
+static const char *argv_diff_tree[] = {"diff-tree", "--pretty", NULL, NULL};
+static const char *argv_checkout[] = {"checkout", "-q", NULL, "--", NULL};
+static const char *argv_show_branch[] = {"show-branch", NULL, NULL};
 
 /* bits #0-15 in revision.h */
 
@@ -398,23 +413,37 @@ struct commit_list *find_bisection(struct commit_list *list,
 	return best;
 }
 
+static void argv_array_push(struct argv_array *array, const char *string)
+{
+	ALLOC_GROW(array->argv, array->argv_nr + 1, array->argv_alloc);
+	array->argv[array->argv_nr++] = string;
+}
+
+static void argv_array_push_sha1(struct argv_array *array,
+				 const unsigned char *sha1,
+				 const char *format)
+{
+	struct strbuf buf = STRBUF_INIT;
+	strbuf_addf(&buf, format, sha1_to_hex(sha1));
+	argv_array_push(array, strbuf_detach(&buf, NULL));
+}
+
+static void sha1_array_push(struct sha1_array *array,
+			    const unsigned char *sha1)
+{
+	ALLOC_GROW(array->sha1, array->sha1_nr + 1, array->sha1_alloc);
+	hashcpy(array->sha1[array->sha1_nr++], sha1);
+}
+
 static int register_ref(const char *refname, const unsigned char *sha1,
 			int flags, void *cb_data)
 {
 	if (!strcmp(refname, "bad")) {
-		ALLOC_GROW(rev_argv, rev_argv_nr + 1, rev_argv_alloc);
-		rev_argv[rev_argv_nr++] = xstrdup(sha1_to_hex(sha1));
+		current_bad_sha1 = sha1;
 	} else if (!prefixcmp(refname, "good-")) {
-		const char *hex = sha1_to_hex(sha1);
-		char *good = xmalloc(strlen(hex) + 2);
-		*good = '^';
-		memcpy(good + 1, hex, strlen(hex) + 1);
-		ALLOC_GROW(rev_argv, rev_argv_nr + 1, rev_argv_alloc);
-		rev_argv[rev_argv_nr++] = good;
+		sha1_array_push(&good_revs, sha1);
 	} else if (!prefixcmp(refname, "skip-")) {
-		ALLOC_GROW(skipped_sha1, skipped_sha1_nr + 1,
-			   skipped_sha1_alloc);
-		hashcpy(skipped_sha1[skipped_sha1_nr++], sha1);
+		sha1_array_push(&skipped_revs, sha1);
 	}
 
 	return 0;
@@ -425,7 +454,7 @@ static int read_bisect_refs(void)
 	return for_each_ref_in("refs/bisect/", register_ref, NULL);
 }
 
-void read_bisect_paths(void)
+void read_bisect_paths(struct argv_array *array)
 {
 	struct strbuf str = STRBUF_INIT;
 	const char *filename = git_path("BISECT_NAMES");
@@ -440,8 +469,8 @@ void read_bisect_paths(void)
 
 		strbuf_trim(&str);
 		quoted = strbuf_detach(&str, NULL);
-		res = sq_dequote_to_argv(quoted, &rev_argv,
-					 &rev_argv_nr, &rev_argv_alloc);
+		res = sq_dequote_to_argv(quoted, &array->argv,
+					 &array->argv_nr, &array->argv_alloc);
 		if (res)
 			die("Badly quoted content in file '%s': %s",
 			    filename, quoted);
@@ -451,26 +480,45 @@ void read_bisect_paths(void)
 	fclose(fp);
 }
 
-static int skipcmp(const void *a, const void *b)
+static int array_cmp(const void *a, const void *b)
 {
 	return hashcmp(a, b);
 }
 
-static void prepare_skipped(void)
+static void sort_sha1_array(struct sha1_array *array)
+{
+	qsort(array->sha1, array->sha1_nr, sizeof(*array->sha1), array_cmp);
+
+	array->sorted = 1;
+}
+
+static const unsigned char *sha1_access(size_t index, void *table)
 {
-	qsort(skipped_sha1, skipped_sha1_nr, sizeof(*skipped_sha1), skipcmp);
+	unsigned char (*array)[20] = table;
+	return array[index];
 }
 
-static const unsigned char *skipped_sha1_access(size_t index, void *table)
+static int lookup_sha1_array(struct sha1_array *array,
+			     const unsigned char *sha1)
 {
-	unsigned char (*skipped)[20] = table;
-	return skipped[index];
+	if (!array->sorted)
+		sort_sha1_array(array);
+
+	return sha1_pos(sha1, array->sha1, array->sha1_nr, sha1_access);
 }
 
-static int lookup_skipped(unsigned char *sha1)
+static char *join_sha1_array_hex(struct sha1_array *array, char delim)
 {
-	return sha1_pos(sha1, skipped_sha1, skipped_sha1_nr,
-			skipped_sha1_access);
+	struct strbuf joined_hexs = STRBUF_INIT;
+	int i;
+
+	for (i = 0; i < array->sha1_nr; i++) {
+		strbuf_addstr(&joined_hexs, sha1_to_hex(array->sha1[i]));
+		if (i + 1 < array->sha1_nr)
+			strbuf_addch(&joined_hexs, delim);
+	}
+
+	return strbuf_detach(&joined_hexs, NULL);
 }
 
 struct commit_list *filter_skipped(struct commit_list *list,
@@ -481,15 +529,14 @@ struct commit_list *filter_skipped(struct commit_list *list,
 
 	*tried = NULL;
 
-	if (!skipped_sha1_nr)
+	if (!skipped_revs.sha1_nr)
 		return list;
 
-	prepare_skipped();
-
 	while (list) {
 		struct commit_list *next = list->next;
 		list->next = NULL;
-		if (0 <= lookup_skipped(list->item->object.sha1)) {
+		if (0 <= lookup_sha1_array(&skipped_revs,
+					   list->item->object.sha1)) {
 			/* Move current to tried list */
 			*tried = list;
 			tried = &list->next;
@@ -508,49 +555,328 @@ struct commit_list *filter_skipped(struct commit_list *list,
 
 static void bisect_rev_setup(struct rev_info *revs, const char *prefix)
 {
+	struct argv_array rev_argv = { NULL, 0, 0 };
+	int i;
+
 	init_revisions(revs, prefix);
 	revs->abbrev = 0;
 	revs->commit_format = CMIT_FMT_UNSPECIFIED;
 
-	/* argv[0] will be ignored by setup_revisions */
-	ALLOC_GROW(rev_argv, rev_argv_nr + 1, rev_argv_alloc);
-	rev_argv[rev_argv_nr++] = xstrdup("bisect_rev_setup");
+	/* rev_argv.argv[0] will be ignored by setup_revisions */
+	argv_array_push(&rev_argv, xstrdup("bisect_rev_setup"));
+	argv_array_push_sha1(&rev_argv, current_bad_sha1, "%s");
+	for (i = 0; i < good_revs.sha1_nr; i++)
+		argv_array_push_sha1(&rev_argv, good_revs.sha1[i], "^%s");
+	argv_array_push(&rev_argv, xstrdup("--"));
+	read_bisect_paths(&rev_argv);
+	argv_array_push(&rev_argv, NULL);
 
-	if (read_bisect_refs())
-		die("reading bisect refs failed");
+	setup_revisions(rev_argv.argv_nr, rev_argv.argv, revs, NULL);
+	revs->limited = 1;
+}
 
-	ALLOC_GROW(rev_argv, rev_argv_nr + 1, rev_argv_alloc);
-	rev_argv[rev_argv_nr++] = xstrdup("--");
+static void bisect_common(struct rev_info *revs, int *reaches, int *all)
+{
+	if (prepare_revision_walk(revs))
+		die("revision walk setup failed");
+	if (revs->tree_objects)
+		mark_edges_uninteresting(revs->commits, revs, NULL);
 
-	read_bisect_paths();
+	revs->commits = find_bisection(revs->commits, reaches, all,
+				       !!skipped_revs.sha1_nr);
+}
 
-	ALLOC_GROW(rev_argv, rev_argv_nr + 1, rev_argv_alloc);
-	rev_argv[rev_argv_nr++] = NULL;
+static void exit_if_skipped_commits(struct commit_list *tried,
+				    const unsigned char *bad)
+{
+	if (!tried)
+		return;
+
+	printf("There are only 'skip'ped commits left to test.\n"
+	       "The first bad commit could be any of:\n");
+	print_commit_list(tried, "%s\n", "%s\n");
+	if (bad)
+		printf("%s\n", sha1_to_hex(bad));
+	printf("We cannot bisect more!\n");
+	exit(2);
+}
 
-	setup_revisions(rev_argv_nr, rev_argv, revs, NULL);
+static int is_expected_rev(const unsigned char *sha1)
+{
+	const char *filename = git_path("BISECT_EXPECTED_REV");
+	struct stat st;
+	struct strbuf str = STRBUF_INIT;
+	FILE *fp;
+	int res = 0;
 
-	revs->limited = 1;
+	if (stat(filename, &st) || !S_ISREG(st.st_mode))
+		return 0;
+
+	fp = fopen(filename, "r");
+	if (!fp)
+		return 0;
+
+	if (strbuf_getline(&str, fp, '\n') != EOF)
+		res = !strcmp(str.buf, sha1_to_hex(sha1));
+
+	strbuf_release(&str);
+	fclose(fp);
+
+	return res;
 }
 
-int bisect_next_vars(const char *prefix)
+static void mark_expected_rev(char *bisect_rev_hex)
+{
+	int len = strlen(bisect_rev_hex);
+	const char *filename = git_path("BISECT_EXPECTED_REV");
+	int fd = open(filename, O_CREAT | O_TRUNC | O_WRONLY, 0600);
+
+	if (fd < 0)
+		die("could not create file '%s': %s",
+		    filename, strerror(errno));
+
+	bisect_rev_hex[len] = '\n';
+	write_or_die(fd, bisect_rev_hex, len + 1);
+	bisect_rev_hex[len] = '\0';
+
+	if (close(fd) < 0)
+		die("closing file %s: %s", filename, strerror(errno));
+}
+
+static int bisect_checkout(char *bisect_rev_hex)
+{
+	int res;
+
+	mark_expected_rev(bisect_rev_hex);
+
+	argv_checkout[2] = bisect_rev_hex;
+	res = run_command_v_opt(argv_checkout, RUN_GIT_CMD);
+	if (res)
+		exit(res);
+
+	argv_show_branch[1] = bisect_rev_hex;
+	return run_command_v_opt(argv_show_branch, RUN_GIT_CMD);
+}
+
+static struct commit *get_commit_reference(const unsigned char *sha1)
+{
+	struct commit *r = lookup_commit_reference(sha1);
+	if (!r)
+		die("Not a valid commit name %s", sha1_to_hex(sha1));
+	return r;
+}
+
+static struct commit **get_bad_and_good_commits(int *rev_nr)
+{
+	int len = 1 + good_revs.sha1_nr;
+	struct commit **rev = xmalloc(len * sizeof(*rev));
+	int i, n = 0;
+
+	rev[n++] = get_commit_reference(current_bad_sha1);
+	for (i = 0; i < good_revs.sha1_nr; i++)
+		rev[n++] = get_commit_reference(good_revs.sha1[i]);
+	*rev_nr = n;
+
+	return rev;
+}
+
+static void handle_bad_merge_base(void)
+{
+	if (is_expected_rev(current_bad_sha1)) {
+		char *bad_hex = sha1_to_hex(current_bad_sha1);
+		char *good_hex = join_sha1_array_hex(&good_revs, ' ');
+
+		fprintf(stderr, "The merge base %s is bad.\n"
+			"This means the bug has been fixed "
+			"between %s and [%s].\n",
+			bad_hex, bad_hex, good_hex);
+
+		exit(3);
+	}
+
+	fprintf(stderr, "Some good revs are not ancestor of the bad rev.\n"
+		"git bisect cannot work properly in this case.\n"
+		"Maybe you mistake good and bad revs?\n");
+	exit(1);
+}
+
+void handle_skipped_merge_base(const unsigned char *mb)
+{
+	char *mb_hex = sha1_to_hex(mb);
+	char *bad_hex = sha1_to_hex(current_bad_sha1);
+	char *good_hex = join_sha1_array_hex(&good_revs, ' ');
+
+	fprintf(stderr, "Warning: the merge base between %s and [%s] "
+		"must be skipped.\n"
+		"So we cannot be sure the first bad commit is "
+		"between %s and %s.\n"
+		"We continue anyway.\n",
+		bad_hex, good_hex, mb_hex, bad_hex);
+	free(good_hex);
+}
+
+/*
+ * "check_merge_bases" checks that merge bases are not "bad".
+ *
+ * - If one is "bad", it means the user assumed something wrong
+ * and we must exit with a non 0 error code.
+ * - If one is "good", that's good, we have nothing to do.
+ * - If one is "skipped", we can't know but we should warn.
+ * - If we don't know, we should check it out and ask the user to test.
+ */
+static void check_merge_bases(void)
+{
+	struct commit_list *result;
+	int rev_nr;
+	struct commit **rev = get_bad_and_good_commits(&rev_nr);
+
+	result = get_merge_bases_many(rev[0], rev_nr - 1, rev + 1, 0);
+
+	for (; result; result = result->next) {
+		const unsigned char *mb = result->item->object.sha1;
+		if (!hashcmp(mb, current_bad_sha1)) {
+			handle_bad_merge_base();
+		} else if (0 <= lookup_sha1_array(&good_revs, mb)) {
+			continue;
+		} else if (0 <= lookup_sha1_array(&skipped_revs, mb)) {
+			handle_skipped_merge_base(mb);
+		} else {
+			printf("Bisecting: a merge base must be tested\n");
+			exit(bisect_checkout(sha1_to_hex(mb)));
+		}
+	}
+
+	free(rev);
+	free_commit_list(result);
+}
+
+/*
+ * This function runs the command "git rev-list $_good ^$_bad"
+ * and returns 1 if it produces some output, 0 otherwise.
+ */
+static int check_ancestors(void)
+{
+	struct argv_array rev_argv = { NULL, 0, 0 };
+	struct strbuf str = STRBUF_INIT;
+	int i, result = 0;
+	struct child_process rls;
+	FILE *rls_fout;
+
+	argv_array_push(&rev_argv, xstrdup("rev-list"));
+	argv_array_push_sha1(&rev_argv, current_bad_sha1, "^%s");
+	for (i = 0; i < good_revs.sha1_nr; i++)
+		argv_array_push_sha1(&rev_argv, good_revs.sha1[i], "%s");
+	argv_array_push(&rev_argv, NULL);
+
+	memset(&rls, 0, sizeof(rls));
+	rls.argv = rev_argv.argv;
+	rls.out = -1;
+	rls.git_cmd = 1;
+	if (start_command(&rls))
+		die("Could not launch 'git rev-list' command.");
+	rls_fout = fdopen(rls.out, "r");
+	while (strbuf_getline(&str, rls_fout, '\n') != EOF) {
+		strbuf_trim(&str);
+		if (*str.buf) {
+			result = 1;
+			break;
+		}
+	}
+	fclose(rls_fout);
+	finish_command(&rls);
+
+	return result;
+}
+
+/*
+ * "check_good_are_ancestors_of_bad" checks that all "good" revs are
+ * ancestor of the "bad" rev.
+ *
+ * If that's not the case, we need to check the merge bases.
+ * If a merge base must be tested by the user, its source code will be
+ * checked out to be tested by the user and we will exit.
+ */
+static void check_good_are_ancestors_of_bad(const char *prefix)
+{
+	const char *filename = git_path("BISECT_ANCESTORS_OK");
+	struct stat st;
+	int fd;
+
+	if (!current_bad_sha1)
+		die("a bad revision is needed");
+
+	/* Check if file BISECT_ANCESTORS_OK exists. */
+	if (!stat(filename, &st) && S_ISREG(st.st_mode))
+		return;
+
+	/* Bisecting with no good rev is ok. */
+	if (good_revs.sha1_nr == 0)
+		return;
+
+	if (check_ancestors())
+		check_merge_bases();
+
+	/* Create file BISECT_ANCESTORS_OK. */
+	fd = open(filename, O_CREAT | O_TRUNC | O_WRONLY, 0600);
+	if (fd < 0)
+		warning("could not create file '%s': %s",
+			filename, strerror(errno));
+	else
+		close(fd);
+}
+
+/*
+ * We use the convention that exiting with an exit code 10 means that
+ * the bisection process finished successfully.
+ * In this case the calling shell script should exit 0.
+ */
+int bisect_next_all(const char *prefix)
 {
 	struct rev_info revs;
-	struct rev_list_info info;
-	int reaches = 0, all = 0;
+	struct commit_list *tried;
+	int reaches = 0, all = 0, nr;
+	const unsigned char *bisect_rev;
+	char bisect_rev_hex[41];
+
+	if (read_bisect_refs())
+		die("reading bisect refs failed");
 
-	memset(&info, 0, sizeof(info));
-	info.revs = &revs;
-	info.bisect_show_flags = BISECT_SHOW_TRIED | BISECT_SHOW_STRINGED;
+	check_good_are_ancestors_of_bad(prefix);
 
 	bisect_rev_setup(&revs, prefix);
 
-	if (prepare_revision_walk(&revs))
-		die("revision walk setup failed");
-	if (revs.tree_objects)
-		mark_edges_uninteresting(revs.commits, &revs, NULL);
+	bisect_common(&revs, &reaches, &all);
+
+	revs.commits = filter_skipped(revs.commits, &tried, 0);
 
-	revs.commits = find_bisection(revs.commits, &reaches, &all,
-				      !!skipped_sha1_nr);
+	if (!revs.commits) {
+		/*
+		 * We should exit here only if the "bad"
+		 * commit is also a "skip" commit.
+		 */
+		exit_if_skipped_commits(tried, NULL);
 
-	return show_bisect_vars(&info, reaches, all);
+		printf("%s was both good and bad\n",
+		       sha1_to_hex(current_bad_sha1));
+		exit(1);
+	}
+
+	bisect_rev = revs.commits->item->object.sha1;
+	memcpy(bisect_rev_hex, sha1_to_hex(bisect_rev), 41);
+
+	if (!hashcmp(bisect_rev, current_bad_sha1)) {
+		exit_if_skipped_commits(tried, current_bad_sha1);
+		printf("%s is first bad commit\n", bisect_rev_hex);
+		argv_diff_tree[2] = bisect_rev_hex;
+		run_command_v_opt(argv_diff_tree, RUN_GIT_CMD);
+		/* This means the bisection process succeeded. */
+		exit(10);
+	}
+
+	nr = all - reaches - 1;
+	printf("Bisecting: %d revisions left to test after this "
+	       "(roughly %d steps)\n", nr, estimate_bisect_steps(all));
+
+	return bisect_checkout(bisect_rev_hex);
 }
+
diff --git a/bisect.h b/bisect.h
index fdba913877..fb744fdb79 100644
--- a/bisect.h
+++ b/bisect.h
@@ -9,10 +9,13 @@ extern struct commit_list *filter_skipped(struct commit_list *list,
 					  struct commit_list **tried,
 					  int show_all);
 
+extern void print_commit_list(struct commit_list *list,
+			      const char *format_cur,
+			      const char *format_last);
+
 /* bisect_show_flags flags in struct rev_list_info */
 #define BISECT_SHOW_ALL		(1<<0)
 #define BISECT_SHOW_TRIED	(1<<1)
-#define BISECT_SHOW_STRINGED	(1<<2)
 
 struct rev_list_info {
 	struct rev_info *revs;
@@ -24,6 +27,8 @@ struct rev_list_info {
 
 extern int show_bisect_vars(struct rev_list_info *info, int reaches, int all);
 
-extern int bisect_next_vars(const char *prefix);
+extern int bisect_next_all(const char *prefix);
+
+extern int estimate_bisect_steps(int all);
 
 #endif
diff --git a/builtin-bisect--helper.c b/builtin-bisect--helper.c
index 8fe778766a..cb3e155116 100644
--- a/builtin-bisect--helper.c
+++ b/builtin-bisect--helper.c
@@ -4,24 +4,24 @@
 #include "bisect.h"
 
 static const char * const git_bisect_helper_usage[] = {
-	"git bisect--helper --next-vars",
+	"git bisect--helper --next-all",
 	NULL
 };
 
 int cmd_bisect__helper(int argc, const char **argv, const char *prefix)
 {
-	int next_vars = 0;
+	int next_all = 0;
 	struct option options[] = {
-		OPT_BOOLEAN(0, "next-vars", &next_vars,
-			    "output next bisect step variables"),
+		OPT_BOOLEAN(0, "next-all", &next_all,
+			    "perform 'git bisect next'"),
 		OPT_END()
 	};
 
 	argc = parse_options(argc, argv, options, git_bisect_helper_usage, 0);
 
-	if (!next_vars)
+	if (!next_all)
 		usage_with_options(git_bisect_helper_usage, options);
 
-	/* next-vars */
-	return bisect_next_vars(prefix);
+	/* next-all */
+	return bisect_next_all(prefix);
 }
diff --git a/builtin-rev-list.c b/builtin-rev-list.c
index 38a8f234de..31ea5f4aac 100644
--- a/builtin-rev-list.c
+++ b/builtin-rev-list.c
@@ -211,7 +211,7 @@ static inline int exp2i(int n)
  *
  * and P(2^n + x) < 0.5 means 2^n < 3x
  */
-static int estimate_bisect_steps(int all)
+int estimate_bisect_steps(int all)
 {
 	int n, x, e;
 
@@ -225,20 +225,37 @@ static int estimate_bisect_steps(int all)
 	return (e < 3 * x) ? n : n - 1;
 }
 
-static void show_tried_revs(struct commit_list *tried, int stringed)
+void print_commit_list(struct commit_list *list,
+		       const char *format_cur,
+		       const char *format_last)
 {
-	printf("bisect_tried='");
-	for (;tried; tried = tried->next) {
-		char *format = tried->next ? "%s|" : "%s";
-		printf(format, sha1_to_hex(tried->item->object.sha1));
+	for ( ; list; list = list->next) {
+		const char *format = list->next ? format_cur : format_last;
+		printf(format, sha1_to_hex(list->item->object.sha1));
 	}
-	printf(stringed ? "' &&\n" : "'\n");
+}
+
+static void show_tried_revs(struct commit_list *tried)
+{
+	printf("bisect_tried='");
+	print_commit_list(tried, "%s|", "%s");
+	printf("'\n");
+}
+
+static void print_var_str(const char *var, const char *val)
+{
+	printf("%s='%s'\n", var, val);
+}
+
+static void print_var_int(const char *var, int val)
+{
+	printf("%s=%d\n", var, val);
 }
 
 int show_bisect_vars(struct rev_list_info *info, int reaches, int all)
 {
 	int cnt, flags = info->bisect_show_flags;
-	char hex[41] = "", *format;
+	char hex[41] = "";
 	struct commit_list *tried;
 	struct rev_info *revs = info->revs;
 
@@ -269,28 +286,14 @@ int show_bisect_vars(struct rev_list_info *info, int reaches, int all)
 	}
 
 	if (flags & BISECT_SHOW_TRIED)
-		show_tried_revs(tried, flags & BISECT_SHOW_STRINGED);
-	format = (flags & BISECT_SHOW_STRINGED) ?
-		"bisect_rev=%s &&\n"
-		"bisect_nr=%d &&\n"
-		"bisect_good=%d &&\n"
-		"bisect_bad=%d &&\n"
-		"bisect_all=%d &&\n"
-		"bisect_steps=%d\n"
-		:
-		"bisect_rev=%s\n"
-		"bisect_nr=%d\n"
-		"bisect_good=%d\n"
-		"bisect_bad=%d\n"
-		"bisect_all=%d\n"
-		"bisect_steps=%d\n";
-	printf(format,
-	       hex,
-	       cnt - 1,
-	       all - reaches - 1,
-	       reaches - 1,
-	       all,
-	       estimate_bisect_steps(all));
+		show_tried_revs(tried);
+
+	print_var_str("bisect_rev", hex);
+	print_var_int("bisect_nr", cnt - 1);
+	print_var_int("bisect_good", all - reaches - 1);
+	print_var_int("bisect_bad", reaches - 1);
+	print_var_int("bisect_all", all);
+	print_var_int("bisect_steps", estimate_bisect_steps(all));
 
 	return 0;
 }
diff --git a/builtin-rev-parse.c b/builtin-rev-parse.c
index 22c6d6ad16..c5b3d6e31b 100644
--- a/builtin-rev-parse.c
+++ b/builtin-rev-parse.c
@@ -402,6 +402,18 @@ static int cmd_parseopt(int argc, const char **argv, const char *prefix)
 	return 0;
 }
 
+static int cmd_sq_quote(int argc, const char **argv)
+{
+	struct strbuf buf = STRBUF_INIT;
+
+	if (argc)
+		sq_quote_argv(&buf, argv, 0);
+	printf("%s\n", buf.buf);
+	strbuf_release(&buf);
+
+	return 0;
+}
+
 static void die_no_single_rev(int quiet)
 {
 	if (quiet)
@@ -419,6 +431,9 @@ int cmd_rev_parse(int argc, const char **argv, const char *prefix)
 	if (argc > 1 && !strcmp("--parseopt", argv[1]))
 		return cmd_parseopt(argc - 1, argv + 1, prefix);
 
+	if (argc > 1 && !strcmp("--sq-quote", argv[1]))
+		return cmd_sq_quote(argc - 2, argv + 2);
+
 	prefix = setup_git_directory();
 	git_config(git_default_config, NULL);
 	for (i = 1; i < argc; i++) {
diff --git a/git-am.sh b/git-am.sh
index 6d1848b6cc..578780be13 100755
--- a/git-am.sh
+++ b/git-am.sh
@@ -44,11 +44,7 @@ else
 fi
 
 sq () {
-	for sqarg
-	do
-		printf "%s" "$sqarg" |
-		sed -e 's/'\''/'\''\\'\'''\''/g' -e 's/.*/ '\''&'\''/'
-	done
+	git rev-parse --sq-quote "$@"
 }
 
 stop_here () {
diff --git a/git-bisect.sh b/git-bisect.sh
index 24712ff304..8969553658 100755
--- a/git-bisect.sh
+++ b/git-bisect.sh
@@ -33,16 +33,6 @@ require_work_tree
 _x40='[0-9a-f][0-9a-f][0-9a-f][0-9a-f][0-9a-f]'
 _x40="$_x40$_x40$_x40$_x40$_x40$_x40$_x40$_x40"
 
-sq() {
-	@@PERL@@ -e '
-		for (@ARGV) {
-			s/'\''/'\'\\\\\'\''/g;
-			print " '\''$_'\''";
-		}
-		print "\n";
-	' "$@"
-}
-
 bisect_autostart() {
 	test -s "$GIT_DIR/BISECT_START" || {
 		echo >&2 'You need to start by "git bisect start"'
@@ -107,7 +97,7 @@ bisect_start() {
 	for arg; do
 	    case "$arg" in --) has_double_dash=1; break ;; esac
 	done
-	orig_args=$(sq "$@")
+	orig_args=$(git rev-parse --sq-quote "$@")
 	bad_seen=0
 	eval=''
 	while [ $# -gt 0 ]; do
@@ -147,7 +137,7 @@ bisect_start() {
 	# Write new start state.
 	#
 	echo "$start_head" >"$GIT_DIR/BISECT_START" &&
-	sq "$@" >"$GIT_DIR/BISECT_NAMES" &&
+	git rev-parse --sq-quote "$@" >"$GIT_DIR/BISECT_NAMES" &&
 	eval "$eval" &&
 	echo "git bisect start$orig_args" >>"$GIT_DIR/BISECT_LOG" || exit
 	#
@@ -177,10 +167,6 @@ is_expected_rev() {
 	test "$1" = $(cat "$GIT_DIR/BISECT_EXPECTED_REV")
 }
 
-mark_expected_rev() {
-	echo "$1" > "$GIT_DIR/BISECT_EXPECTED_REV"
-}
-
 check_expected_revs() {
 	for _rev in "$@"; do
 		if ! is_expected_rev "$_rev"; then
@@ -199,7 +185,7 @@ bisect_skip() {
             *..*)
                 revs=$(git rev-list "$arg") || die "Bad rev input: $arg" ;;
             *)
-                revs=$(sq "$arg") ;;
+                revs=$(git rev-parse --sq-quote "$arg") ;;
 	    esac
             all="$all $revs"
         done
@@ -279,162 +265,22 @@ bisect_auto_next() {
 	bisect_next_check && bisect_next || :
 }
 
-exit_if_skipped_commits () {
-	_tried=$1
-	_bad=$2
-	if test -n "$_tried" ; then
-		echo "There are only 'skip'ped commit left to test."
-		echo "The first bad commit could be any of:"
-		echo "$_tried" | tr '[|]' '[\012]'
-		test -n "$_bad" && echo "$_bad"
-		echo "We cannot bisect more!"
-		exit 2
-	fi
-}
-
-bisect_checkout() {
-	_rev="$1"
-	_msg="$2"
-	echo "Bisecting: $_msg"
-	mark_expected_rev "$_rev"
-	git checkout -q "$_rev" -- || exit
-	git show-branch "$_rev"
-}
-
-is_among() {
-	_rev="$1"
-	_list="$2"
-	case "$_list" in *$_rev*) return 0 ;; esac
-	return 1
-}
-
-handle_bad_merge_base() {
-	_badmb="$1"
-	_good="$2"
-	if is_expected_rev "$_badmb"; then
-		cat >&2 <<EOF
-The merge base $_badmb is bad.
-This means the bug has been fixed between $_badmb and [$_good].
-EOF
-		exit 3
-	else
-		cat >&2 <<EOF
-Some good revs are not ancestor of the bad rev.
-git bisect cannot work properly in this case.
-Maybe you mistake good and bad revs?
-EOF
-		exit 1
-	fi
-}
-
-handle_skipped_merge_base() {
-	_mb="$1"
-	_bad="$2"
-	_good="$3"
-	cat >&2 <<EOF
-Warning: the merge base between $_bad and [$_good] must be skipped.
-So we cannot be sure the first bad commit is between $_mb and $_bad.
-We continue anyway.
-EOF
-}
-
-#
-# "check_merge_bases" checks that merge bases are not "bad".
-#
-# - If one is "good", that's good, we have nothing to do.
-# - If one is "bad", it means the user assumed something wrong
-# and we must exit.
-# - If one is "skipped", we can't know but we should warn.
-# - If we don't know, we should check it out and ask the user to test.
-#
-# In the last case we will return 1, and otherwise 0.
-#
-check_merge_bases() {
-	_bad="$1"
-	_good="$2"
-	_skip="$3"
-	for _mb in $(git merge-base --all $_bad $_good)
-	do
-		if is_among "$_mb" "$_good"; then
-			continue
-		elif test "$_mb" = "$_bad"; then
-			handle_bad_merge_base "$_bad" "$_good"
-		elif is_among "$_mb" "$_skip"; then
-			handle_skipped_merge_base "$_mb" "$_bad" "$_good"
-		else
-			bisect_checkout "$_mb" "a merge base must be tested"
-			return 1
-		fi
-	done
-	return 0
-}
-
-#
-# "check_good_are_ancestors_of_bad" checks that all "good" revs are
-# ancestor of the "bad" rev.
-#
-# If that's not the case, we need to check the merge bases.
-# If a merge base must be tested by the user we return 1 and
-# otherwise 0.
-#
-check_good_are_ancestors_of_bad() {
-	test -f "$GIT_DIR/BISECT_ANCESTORS_OK" &&
-		return
-
-	_bad="$1"
-	_good=$(echo $2 | sed -e 's/\^//g')
-	_skip="$3"
-
-	# Bisecting with no good rev is ok
-	test -z "$_good" && return
-
-	_side=$(git rev-list $_good ^$_bad)
-	if test -n "$_side"; then
-		# Return if a checkout was done
-		check_merge_bases "$_bad" "$_good" "$_skip" || return
-	fi
-
-	: > "$GIT_DIR/BISECT_ANCESTORS_OK"
-
-	return 0
-}
-
 bisect_next() {
 	case "$#" in 0) ;; *) usage ;; esac
 	bisect_autostart
 	bisect_next_check good
 
-	# Get bad, good and skipped revs
-	bad=$(git rev-parse --verify refs/bisect/bad) &&
-	good=$(git for-each-ref --format='^%(objectname)' \
-		"refs/bisect/good-*" | tr '\012' ' ') &&
-	skip=$(git for-each-ref --format='%(objectname)' \
-		"refs/bisect/skip-*" | tr '\012' ' ') || exit
-
-	# Maybe some merge bases must be tested first
-	check_good_are_ancestors_of_bad "$bad" "$good" "$skip"
-	# Return now if a checkout has already been done
-	test "$?" -eq "1" && return
-
-	# Get bisection information
-	eval=$(eval "git bisect--helper --next-vars") &&
-	eval "$eval" || exit
-
-	if [ -z "$bisect_rev" ]; then
-		# We should exit here only if the "bad"
-		# commit is also a "skip" commit (see above).
-		exit_if_skipped_commits "$bisect_tried"
-		echo "$bad was both good and bad"
-		exit 1
-	fi
-	if [ "$bisect_rev" = "$bad" ]; then
-		exit_if_skipped_commits "$bisect_tried" "$bad"
-		echo "$bisect_rev is first bad commit"
-		git diff-tree --pretty $bisect_rev
-		exit 0
-	fi
+	# Perform all bisection computation, display and checkout
+	git bisect--helper --next-all
+	res=$?
+
+        # Check if we should exit because bisection is finished
+	test $res -eq 10 && exit 0
 
-	bisect_checkout "$bisect_rev" "$bisect_nr revisions left to test after this (roughly $bisect_steps steps)"
+	# Check for an error in the bisection process
+	test $res -ne 0 && exit $res
+
+	return 0
 }
 
 bisect_visualize() {