[PATCH v4 0/7] add --ff option to cherry-pick

@@ -0,0 +1,98 @@
+#!/bin/sh
+
+test_description='test cherry-picking with --ff option'
+
+. ./test-lib.sh
+
+test_expect_success setup '
+	echo first > file1 &&
+	git add file1 &&
+	test_tick &&
+	git commit -m "first" &&
+	git tag first &&
+
+	git checkout -b other &&
+	echo second >> file1 &&
+	git add file1 &&
+	test_tick &&
+	git commit -m "second" &&
+	git tag second
+'
+
+test_expect_success 'cherry-pick using --ff fast forwards' '
+	git checkout master &&
+	git reset --hard first &&
+	test_tick &&
+	git cherry-pick --ff second &&
+	test "$(git rev-parse --verify HEAD)" = "$(git rev-parse --verify second)"
+'
+
+test_expect_success 'cherry-pick not using --ff does not fast forwards' '
+	git checkout master &&
+	git reset --hard first &&
+	test_tick &&
+	git cherry-pick second &&
+	test "$(git rev-parse --verify HEAD)" != "$(git rev-parse --verify second)"
+'
+
+#
+# We setup the following graph:
+#
+#	      B---C
+#	     /   /
+#	first---A
+#
+# (This has been taken from t3502-cherry-pick-merge.sh)
+#
+test_expect_success 'merge setup' '
+	git checkout master &&
+	git reset --hard first &&
+	echo new line >A &&
+	git add A &&
+	test_tick &&
+	git commit -m "add line to A" A &&
+	git tag A &&
+	git checkout -b side first &&
+	echo new line >B &&
+	git add B &&
+	test_tick &&
+	git commit -m "add line to B" B &&
+	git tag B &&
+	git checkout master &&
+	git merge side &&
+	git tag C &&
+	git checkout -b new A
+'
+
+test_expect_success 'cherry-pick a non-merge with --ff and -m should fail' '
+	git reset --hard A -- &&
+	test_must_fail git cherry-pick --ff -m 1 B &&
+	git diff --exit-code A --
+'
+
+test_expect_success 'cherry pick a merge with --ff but without -m should fail' '
+	git reset --hard A -- &&
+	test_must_fail git cherry-pick --ff C &&
+	git diff --exit-code A --
+'
+
+test_expect_success 'cherry pick with --ff a merge (1)' '
+	git reset --hard A -- &&
+	git cherry-pick --ff -m 1 C &&
+	git diff --exit-code C &&
+	test "$(git rev-parse --verify HEAD)" = "$(git rev-parse --verify C)"
+'
+
+test_expect_success 'cherry pick with --ff a merge (2)' '
+	git reset --hard B -- &&
+	git cherry-pick --ff -m 2 C &&
+	git diff --exit-code C &&
+	test "$(git rev-parse --verify HEAD)" = "$(git rev-parse --verify C)"
+'
+
+test_expect_success 'cherry pick a merge relative to nonexistent parent with --ff should fail' '
+	git reset --hard B -- &&
+	test_must_fail git cherry-pick --ff -m 3 C
+'
+
+test_done

@@ -13,6 +13,7 @@
 #include "revision.h"
 #include "rerere.h"
 #include "merge-recursive.h"
+#include "refs.h"
 
 /*
  * This implements the builtins revert and cherry-pick.

@@ -35,7 +36,7 @@ static const char * const cherry_pick_usage[] = {
 	NULL
 };
 
-static int edit, no_replay, no_commit, mainline, signoff;
+static int edit, no_replay, no_commit, mainline, signoff, allow_ff;
 static enum { REVERT, CHERRY_PICK } action;
 static struct commit *commit;
 static const char *commit_name;

@@ -60,8 +61,19 @@ static void parse_args(int argc, const char **argv)
 		OPT_INTEGER('m', "mainline", &mainline, "parent number"),
 		OPT_RERERE_AUTOUPDATE(&allow_rerere_auto),
 		OPT_END(),
+		OPT_END(),
+		OPT_END(),
 	};
 
+	if (action == CHERRY_PICK) {
+		struct option cp_extra[] = {
+			OPT_BOOLEAN(0, "ff", &allow_ff, "allow fast-forward"),
+			OPT_END(),
+		};
+		if (parse_options_concat(options, ARRAY_SIZE(options), cp_extra))
+			die("program error");
+	}
+
 	if (parse_options(argc, argv, NULL, options, usage_str, 0) != 1)
 		usage_with_options(usage_str, options);
 

@@ -244,6 +256,17 @@ static NORETURN void die_dirty_index(const char *me)
 	}
 }
 
+static int fast_forward_to(const unsigned char *to, const unsigned char *from)
+{
+	struct ref_lock *ref_lock;
+
+	read_cache();
+	if (checkout_fast_forward(from, to))
+		exit(1); /* the callee should have complained already */
+	ref_lock = lock_any_ref_for_update("HEAD", from, 0);
+	return write_ref_sha1(ref_lock, to, "cherry-pick");
+}
+
 static int revert_or_cherry_pick(int argc, const char **argv)
 {
 	unsigned char head[20];

@@ -265,6 +288,17 @@ static int revert_or_cherry_pick(int argc, const char **argv)
 	if (action == REVERT && !no_replay)
 		die("revert is incompatible with replay");
 
+	if (allow_ff) {
+		if (signoff)
+			die("cherry-pick --ff cannot be used with --signoff");
+		if (no_commit)
+			die("cherry-pick --ff cannot be used with --no-commit");
+		if (no_replay)
+			die("cherry-pick --ff cannot be used with -x");
+		if (edit)
+			die("cherry-pick --ff cannot be used with --edit");
+	}
+
 	if (read_cache() < 0)
 		die("git %s: failed to read the index", me);
 	if (no_commit) {

@@ -284,8 +318,6 @@ static int revert_or_cherry_pick(int argc, const char **argv)
 	}
 	discard_cache();
 
-	index_fd = hold_locked_index(&index_lock, 1);
-
 	if (!commit->parents) {
 		if (action == REVERT)
 			die ("Cannot revert a root commit");

@@ -314,6 +346,9 @@ static int revert_or_cherry_pick(int argc, const char **argv)
 	else
 		parent = commit->parents->item;
 
+	if (allow_ff && !hashcmp(parent->object.sha1, head))
+		return fast_forward_to(commit->object.sha1, head);
+
 	if (!(message = commit->buffer))
 		die ("Cannot get commit message for %s",
 				sha1_to_hex(commit->object.sha1));

@@ -343,6 +378,8 @@ static int revert_or_cherry_pick(int argc, const char **argv)
 
 	oneline = get_oneline(message);
 
+	index_fd = hold_locked_index(&index_lock, 1);
+
 	if (action == REVERT) {
 		char *oneline_body = strchr(oneline, ' ');
 

@@ -222,8 +222,8 @@ do_with_author () {
 }
 
 pick_one () {
-	no_ff=
-	case "$1" in -n) sha1=$2; no_ff=t ;; *) sha1=$1 ;; esac
+	ff=--ff
+	case "$1" in -n) sha1=$2; ff= ;; *) sha1=$1 ;; esac
 	output git rev-parse --verify $sha1 || die "Invalid commit name: $sha1"
 	test -d "$REWRITTEN" &&
 		pick_one_preserving_merges "$@" && return

@@ -232,16 +232,7 @@ pick_one () {
 		output git cherry-pick "$@"
 		return
 	fi
-	parent_sha1=$(git rev-parse --verify $sha1^) ||
-		die "Could not get the parent of $sha1"
-	current_sha1=$(git rev-parse --verify HEAD)
-	if test -z "$no_ff" && test "$current_sha1" = "$parent_sha1"
-	then
-		output git reset --hard $sha1
-		output warn Fast-forward to $(git rev-parse --short $sha1)
-	else
-		output git cherry-pick "$@"
-	fi
+	output git cherry-pick $ff "$@"
 }
 
 pick_one_preserving_merges () {

@@ -667,7 +667,7 @@ static int count_unmerged_entries(void)
 	return ret;
 }
 
-static int checkout_fast_forward(unsigned char *head, unsigned char *remote)
+int checkout_fast_forward(const unsigned char *head, const unsigned char *remote)
 {
 	struct tree *trees[MAX_UNPACK_TREES];
 	struct unpack_trees_options opts;

@@ -1054,4 +1054,7 @@ void overlay_tree_on_cache(const char *tree_name, const char *prefix);
 char *alias_lookup(const char *alias);
 int split_cmdline(char *cmdline, const char ***argv);
 
+/* builtin/merge.c */
+int checkout_fast_forward(const unsigned char *from, const unsigned char *to);
+
 #endif /* CACHE_H */

@@ -7,7 +7,7 @@ git-cherry-pick - Apply the change introduced by an existing commit
 
 SYNOPSIS
 --------
-'git cherry-pick' [--edit] [-n] [-m parent-number] [-s] [-x] [--ff] <commit>
+'git cherry-pick' [--edit] [-n] [-m parent-number] [-s] [-x] [--[no-]ff] <commit>
 
 DESCRIPTION
 -----------

@@ -75,6 +75,10 @@ effect to your index in a row.
 	cherry-pick'ed commit, then a fast forward to this commit will
 	be performed.
 
+--no-ff::
+	Does nothing right now, but in the future this may disallow
+	fast forward if it becomes the default behavior.
+
 Author
 ------
 Written by Junio C Hamano <gitster@pobox.com>

@@ -36,7 +36,7 @@ static const char * const cherry_pick_usage[] = {
 	NULL
 };
 
-static int edit, no_replay, no_commit, mainline, signoff, allow_ff;
+static int edit, no_replay, no_commit, mainline, signoff, allow_ff, no_ff;
 static enum { REVERT, CHERRY_PICK } action;
 static struct commit *commit;
 static const char *commit_name;

@@ -63,11 +63,13 @@ static void parse_args(int argc, const char **argv)
 		OPT_END(),
 		OPT_END(),
 		OPT_END(),
+		OPT_END(),
 	};
 
 	if (action == CHERRY_PICK) {
 		struct option cp_extra[] = {
 			OPT_BOOLEAN(0, "ff", &allow_ff, "allow fast-forward"),
+			OPT_BOOLEAN(0, "no-ff", &no_ff, "disallow fast forward"),
 			OPT_END(),
 		};
 		if (parse_options_concat(options, ARRAY_SIZE(options), cp_extra))

@@ -297,6 +299,8 @@ static int revert_or_cherry_pick(int argc, const char **argv)
 			die("cherry-pick --ff cannot be used with -x");
 		if (edit)
 			die("cherry-pick --ff cannot be used with --edit");
+		if (no_ff)
+			die("cherry-pick --ff cannot be used with --no-ff");
 	}
 
 	if (read_cache() < 0)

@@ -35,6 +35,14 @@ test_expect_success 'cherry-pick not using --ff does not fast forwards' '
 	test "$(git rev-parse --verify HEAD)" != "$(git rev-parse --verify second)"
 '
 
+test_expect_success 'cherry-pick using --no-ff does not fast forwards' '
+	git checkout master &&
+	git reset --hard first &&
+	test_tick &&
+	git cherry-pick --no-ff second &&
+	test "$(git rev-parse --verify HEAD)" != "$(git rev-parse --verify second)"
+'
+
 #
 # We setup the following graph:
 #

@@ -659,3 +659,18 @@ int parse_opt_tertiary(const struct option *opt, const char *arg, int unset)
 	*target = unset ? 2 : 1;
 	return 0;
 }
+
+int parse_options_concat(struct option *dst, size_t dst_size, struct option *src)
+{
+	int i, j;
+
+	for (i = 0; i < dst_size; i++)
+		if (dst[i].type == OPTION_END)
+			break;
+	for (j = 0; i < dst_size; i++, j++) {
+		dst[i] = src[j];
+		if (src[j].type == OPTION_END)
+			return 0;
+	}
+	return -1;
+}

@@ -187,6 +187,7 @@ extern int parse_options_step(struct parse_opt_ctx_t *ctx,
 
 extern int parse_options_end(struct parse_opt_ctx_t *ctx);
 
+extern int parse_options_concat(struct option *dst, size_t, struct option *src);
 
 /*----- some often used options -----*/
 extern int parse_opt_abbrev_cb(const struct option *, const char *, int);

@@ -7,7 +7,7 @@ git-cherry-pick - Apply the change introduced by an existing commit
 
 SYNOPSIS
 --------
-'git cherry-pick' [--edit] [-n] [-m parent-number] [-s] [-x] <commit>
+'git cherry-pick' [--edit] [-n] [-m parent-number] [-s] [-x] [--ff] <commit>
 
 DESCRIPTION
 -----------

@@ -70,6 +70,10 @@ effect to your index in a row.
 --signoff::
 	Add Signed-off-by line at the end of the commit message.
 
+--ff::
+	If the current HEAD is the same as the parent of the
+	cherry-pick'ed commit, then a fast forward to this commit will
+	be performed.
 
 Author
 ------