Merge branch 'cc/reset-keep'

* cc/reset-keep:
  Documentation: improve description of "git reset --keep"
  reset: disallow using --keep when there are unmerged entries
  reset: disallow "reset --keep" outside a work tree
  Documentation: reset: describe new "--keep" option
  reset: add test cases for "--keep" option
  reset: add option "--keep" to "git reset"

5 files changed, 229 insertions, 20 deletions

diff --git a/Documentation/git-reset.txt b/Documentation/git-reset.txt
index 168db08627..645f0c1748 100644
--- a/Documentation/git-reset.txt
+++ b/Documentation/git-reset.txt
@@ -8,7 +8,7 @@ git-reset - Reset current HEAD to the specified state
 SYNOPSIS
 --------
 [verse]
-'git reset' [--mixed | --soft | --hard | --merge] [-q] [<commit>]
+'git reset' [--mixed | --soft | --hard | --merge | --keep] [-q] [<commit>]
 'git reset' [-q] [<commit>] [--] <paths>...
 'git reset' --patch [<commit>] [--] [<paths>...]
 
@@ -52,6 +52,14 @@ OPTIONS
 	and updates the files that are different between the named commit
 	and the current commit in the working tree.
 
+--keep::
+	Reset the index to the given commit, keeping local changes in
+	the working tree since the current commit, while updating
+	working tree files without local changes to what appears in
+	the given commit.  If a file that is different between the
+	current commit and the given commit has local changes, reset
+	is aborted.
+
 -p::
 --patch::
 	Interactively select hunks in the difference between the index
@@ -93,6 +101,7 @@ in the index and in state D in HEAD.
 				--mixed  A       D     D
 				--hard   D       D     D
 				--merge (disallowed)
+				--keep  (disallowed)
 
       working index HEAD target         working index HEAD
       ----------------------------------------------------
@@ -100,6 +109,7 @@ in the index and in state D in HEAD.
 				--mixed  A       C     C
 				--hard   C       C     C
 				--merge (disallowed)
+				--keep   A       C     C
 
       working index HEAD target         working index HEAD
       ----------------------------------------------------
@@ -107,6 +117,7 @@ in the index and in state D in HEAD.
 				--mixed  B       D     D
 				--hard   D       D     D
 				--merge  D       D     D
+				--keep  (disallowed)
 
       working index HEAD target         working index HEAD
       ----------------------------------------------------
@@ -114,6 +125,7 @@ in the index and in state D in HEAD.
 				--mixed  B       C     C
 				--hard   C       C     C
 				--merge  C       C     C
+				--keep   B       C     C
 
       working index HEAD target         working index HEAD
       ----------------------------------------------------
@@ -121,6 +133,7 @@ in the index and in state D in HEAD.
 				--mixed  B       D     D
 				--hard   D       D     D
 				--merge (disallowed)
+				--keep  (disallowed)
 
       working index HEAD target         working index HEAD
       ----------------------------------------------------
@@ -128,6 +141,7 @@ in the index and in state D in HEAD.
 				--mixed  B       C     C
 				--hard   C       C     C
 				--merge  B       C     C
+				--keep   B       C     C
 
 "reset --merge" is meant to be used when resetting out of a conflicted
 merge. Any mergy operation guarantees that the work tree file that is
@@ -138,6 +152,15 @@ between the index and the work tree, then it means that we are not
 resetting out from a state that a mergy operation left after failing
 with a conflict. That is why we disallow --merge option in this case.
 
+"reset --keep" is meant to be used when removing some of the last
+commits in the current branch while keeping changes in the working
+tree. If there could be conflicts between the changes in the commit we
+want to remove and the changes in the working tree we want to keep,
+the reset is disallowed. That's why it is disallowed if there are both
+changes between the working tree and HEAD, and between HEAD and the
+target. To be safe, it is also disallowed when there are unmerged
+entries.
+
 The following tables show what happens when there are unmerged
 entries:
 
@@ -147,6 +170,7 @@ entries:
 				--mixed  X       B     B
 				--hard   B       B     B
 				--merge  B       B     B
+				--keep  (disallowed)
 
       working index HEAD target         working index HEAD
       ----------------------------------------------------
@@ -154,6 +178,7 @@ entries:
 				--mixed  X       A     A
 				--hard   A       A     A
 				--merge  A       A     A
+				--keep  (disallowed)
 
 X means any state and U means an unmerged index.
 
@@ -325,6 +350,32 @@ $ git add frotz.c                           <3>
 <2> This commits all other changes in the index.
 <3> Adds the file to the index again.
 
+Keep changes in working tree while discarding some previous commits::
++
+Suppose you are working on something and you commit it, and then you
+continue working a bit more, but now you think that what you have in
+your working tree should be in another branch that has nothing to do
+with what you commited previously. You can start a new branch and
+reset it while keeping the changes in your work tree.
++
+------------
+$ git tag start
+$ git checkout -b branch1
+$ edit
+$ git commit ...                            <1>
+$ edit
+$ git checkout -b branch2                   <2>
+$ git reset --keep start                    <3>
+------------
++
+<1> This commits your first edits in branch1.
+<2> In the ideal world, you could have realized that the earlier
+    commit did not belong to the new topic when you created and switched
+    to branch2 (i.e. "git checkout -b branch2 start"), but nobody is
+    perfect.
+<3> But you can use "reset --keep" to remove the unwanted commit after
+    you switched to "branch2".
+
 Author
 ------
 Written by Junio C Hamano <gitster@pobox.com> and Linus Torvalds <torvalds@osdl.org>
diff --git a/builtin/reset.c b/builtin/reset.c
index 0f5022eed2..2c3a69adc6 100644
--- a/builtin/reset.c
+++ b/builtin/reset.c
@@ -22,13 +22,15 @@
 #include "cache-tree.h"
 
 static const char * const git_reset_usage[] = {
-	"git reset [--mixed | --soft | --hard | --merge] [-q] [<commit>]",
+	"git reset [--mixed | --soft | --hard | --merge | --keep] [-q] [<commit>]",
 	"git reset [--mixed] <commit> [--] <paths>...",
 	NULL
 };
 
-enum reset_type { MIXED, SOFT, HARD, MERGE, NONE };
-static const char *reset_type_names[] = { "mixed", "soft", "hard", "merge", NULL };
+enum reset_type { MIXED, SOFT, HARD, MERGE, KEEP, NONE };
+static const char *reset_type_names[] = {
+	"mixed", "soft", "hard", "merge", "keep", NULL
+};
 
 static char *args_to_str(const char **argv)
 {
@@ -71,6 +73,7 @@ static int reset_index_file(const unsigned char *sha1, int reset_type, int quiet
 	if (!quiet)
 		opts.verbose_update = 1;
 	switch (reset_type) {
+	case KEEP:
 	case MERGE:
 		opts.update = 1;
 		break;
@@ -85,6 +88,16 @@ static int reset_index_file(const unsigned char *sha1, int reset_type, int quiet
 
 	read_cache_unmerged();
 
+	if (reset_type == KEEP) {
+		unsigned char head_sha1[20];
+		if (get_sha1("HEAD", head_sha1))
+			return error("You do not have a valid HEAD.");
+		if (!fill_tree_descriptor(desc, head_sha1))
+			return error("Failed to find tree of HEAD.");
+		nr++;
+		opts.fn = twoway_merge;
+	}
+
 	if (!fill_tree_descriptor(desc + nr - 1, sha1))
 		return error("Failed to find tree of %s.", sha1_to_hex(sha1));
 	if (unpack_trees(nr, desc, &opts))
@@ -211,6 +224,14 @@ static void prepend_reflog_action(const char *action, char *buf, size_t size)
 		warning("Reflog action message too long: %.*s...", 50, buf);
 }
 
+static void die_if_unmerged_cache(int reset_type)
+{
+	if (is_merge() || read_cache() < 0 || unmerged_cache())
+		die("Cannot do a %s reset in the middle of a merge.",
+		    reset_type_names[reset_type]);
+
+}
+
 int cmd_reset(int argc, const char **argv, const char *prefix)
 {
 	int i = 0, reset_type = NONE, update_ref_status = 0, quiet = 0;
@@ -229,6 +250,8 @@ int cmd_reset(int argc, const char **argv, const char *prefix)
 				"reset HEAD, index and working tree", HARD),
 		OPT_SET_INT(0, "merge", &reset_type,
 				"reset HEAD, index and working tree", MERGE),
+		OPT_SET_INT(0, "keep", &reset_type,
+				"reset HEAD but keep local changes", KEEP),
 		OPT_BOOLEAN('p', "patch", &patch_mode, "select hunks interactively"),
 		OPT_END()
 	};
@@ -304,7 +327,7 @@ int cmd_reset(int argc, const char **argv, const char *prefix)
 	if (reset_type == NONE)
 		reset_type = MIXED; /* by default */
 
-	if (reset_type == HARD || reset_type == MERGE)
+	if (reset_type != SOFT && reset_type != MIXED)
 		setup_work_tree();
 
 	if (reset_type == MIXED && is_bare_repository())
@@ -314,12 +337,18 @@ int cmd_reset(int argc, const char **argv, const char *prefix)
 	/* Soft reset does not touch the index file nor the working tree
 	 * at all, but requires them in a good order.  Other resets reset
 	 * the index file to the tree object we are switching to. */
-	if (reset_type == SOFT) {
-		if (is_merge() || read_cache() < 0 || unmerged_cache())
-			die("Cannot do a soft reset in the middle of a merge.");
+	if (reset_type == SOFT)
+		die_if_unmerged_cache(reset_type);
+	else {
+		int err;
+		if (reset_type == KEEP)
+			die_if_unmerged_cache(reset_type);
+		err = reset_index_file(sha1, reset_type, quiet);
+		if (reset_type == KEEP)
+			err = err || reset_index_file(sha1, MIXED, quiet);
+		if (err)
+			die("Could not reset index file to revision '%s'.", rev);
 	}
-	else if (reset_index_file(sha1, reset_type, quiet))
-		die("Could not reset index file to revision '%s'.", rev);
 
 	/* Any resets update HEAD to the head being switched to,
 	 * saving the previous head in ORIG_HEAD before. */
diff --git a/t/t7103-reset-bare.sh b/t/t7103-reset-bare.sh
index afb55b3a46..1eef93c2b2 100755
--- a/t/t7103-reset-bare.sh
+++ b/t/t7103-reset-bare.sh
@@ -11,21 +11,26 @@ test_expect_success 'setup non-bare' '
 	git commit -a -m two
 '
 
-test_expect_success 'hard reset requires a worktree' '
+test_expect_success '"hard" reset requires a worktree' '
 	(cd .git &&
 	 test_must_fail git reset --hard)
 '
 
-test_expect_success 'merge reset requires a worktree' '
+test_expect_success '"merge" reset requires a worktree' '
 	(cd .git &&
 	 test_must_fail git reset --merge)
 '
 
-test_expect_success 'mixed reset is ok' '
+test_expect_success '"keep" reset requires a worktree' '
+	(cd .git &&
+	 test_must_fail git reset --keep)
+'
+
+test_expect_success '"mixed" reset is ok' '
 	(cd .git && git reset)
 '
 
-test_expect_success 'soft reset is ok' '
+test_expect_success '"soft" reset is ok' '
 	(cd .git && git reset --soft)
 '
 
@@ -40,19 +45,23 @@ test_expect_success 'setup bare' '
 	cd bare.git
 '
 
-test_expect_success 'hard reset is not allowed in bare' '
+test_expect_success '"hard" reset is not allowed in bare' '
 	test_must_fail git reset --hard HEAD^
 '
 
-test_expect_success 'merge reset is not allowed in bare' '
+test_expect_success '"merge" reset is not allowed in bare' '
 	test_must_fail git reset --merge HEAD^
 '
 
-test_expect_success 'mixed reset is not allowed in bare' '
+test_expect_success '"keep" reset is not allowed in bare' '
+	test_must_fail git reset --keep HEAD^
+'
+
+test_expect_success '"mixed" reset is not allowed in bare' '
 	test_must_fail git reset --mixed HEAD^
 '
 
-test_expect_success 'soft reset is allowed in bare' '
+test_expect_success '"soft" reset is allowed in bare' '
 	git reset --soft HEAD^ &&
 	test "`git show --pretty=format:%s | head -n 1`" = "one"
 '
diff --git a/t/t7110-reset-merge.sh b/t/t7110-reset-merge.sh
index 8704d00196..70cdd8e618 100755
--- a/t/t7110-reset-merge.sh
+++ b/t/t7110-reset-merge.sh
@@ -3,7 +3,7 @@
 # Copyright (c) 2009 Christian Couder
 #
 
-test_description='Tests for "git reset --merge"'
+test_description='Tests for "git reset" with "--merge" and "--keep" options'
 
 . ./test-lib.sh
 
@@ -47,6 +47,30 @@ test_expect_success 'reset --merge is ok when switching back' '
 #
 #           working index HEAD target         working index HEAD
 #           ----------------------------------------------------
+# file1:     C       C     C    D     --keep   D       D     D
+# file2:     C       D     D    D     --keep   C       D     D
+test_expect_success 'reset --keep is ok with changes in file it does not touch' '
+    git reset --hard second &&
+    cat file1 >file2 &&
+    git reset --keep HEAD^ &&
+    ! grep 4 file1 &&
+    grep 4 file2 &&
+    test "$(git rev-parse HEAD)" = "$(git rev-parse initial)" &&
+    test -z "$(git diff --cached)"
+'
+
+test_expect_success 'reset --keep is ok when switching back' '
+    git reset --keep second &&
+    grep 4 file1 &&
+    grep 4 file2 &&
+    test "$(git rev-parse HEAD)" = "$(git rev-parse second)" &&
+    test -z "$(git diff --cached)"
+'
+
+# The next test will test the following:
+#
+#           working index HEAD target         working index HEAD
+#           ----------------------------------------------------
 # file1:     B       B     C    D     --merge  D       D     D
 # file2:     C       D     D    D     --merge  C       D     D
 test_expect_success 'reset --merge discards changes added to index (1)' '
@@ -78,6 +102,18 @@ test_expect_success 'reset --merge is ok again when switching back (1)' '
 #
 #           working index HEAD target         working index HEAD
 #           ----------------------------------------------------
+# file1:     B       B     C    D     --keep   (disallowed)
+test_expect_success 'reset --keep fails with changes in index in files it touches' '
+    git reset --hard second &&
+    echo "line 5" >> file1 &&
+    git add file1 &&
+    test_must_fail git reset --keep HEAD^
+'
+
+# The next test will test the following:
+#
+#           working index HEAD target         working index HEAD
+#           ----------------------------------------------------
 # file1:     C       C     C    D     --merge  D       D     D
 # file2:     C       C     D    D     --merge  D       D     D
 test_expect_success 'reset --merge discards changes added to index (2)' '
@@ -104,6 +140,30 @@ test_expect_success 'reset --merge is ok again when switching back (2)' '
 #
 #           working index HEAD target         working index HEAD
 #           ----------------------------------------------------
+# file1:     C       C     C    D     --keep   D       D     D
+# file2:     C       C     D    D     --keep   C       D     D
+test_expect_success 'reset --keep keeps changes it does not touch' '
+    git reset --hard second &&
+    echo "line 4" >> file2 &&
+    git add file2 &&
+    git reset --keep HEAD^ &&
+    grep 4 file2 &&
+    test "$(git rev-parse HEAD)" = "$(git rev-parse initial)" &&
+    test -z "$(git diff --cached)"
+'
+
+test_expect_success 'reset --keep keeps changes when switching back' '
+    git reset --keep second &&
+    grep 4 file2 &&
+    grep 4 file1 &&
+    test "$(git rev-parse HEAD)" = "$(git rev-parse second)" &&
+    test -z "$(git diff --cached)"
+'
+
+# The next test will test the following:
+#
+#           working index HEAD target         working index HEAD
+#           ----------------------------------------------------
 # file1:     A       B     B    C     --merge  (disallowed)
 test_expect_success 'reset --merge fails with changes in file it touches' '
     git reset --hard second &&
@@ -116,6 +176,22 @@ test_expect_success 'reset --merge fails with changes in file it touches' '
     grep file1 err.log | grep "not uptodate"
 '
 
+# The next test will test the following:
+#
+#           working index HEAD target         working index HEAD
+#           ----------------------------------------------------
+# file1:     A       B     B    C     --keep   (disallowed)
+test_expect_success 'reset --keep fails with changes in file it touches' '
+    git reset --hard second &&
+    echo "line 5" >> file1 &&
+    test_tick &&
+    git commit -m "add line 5" file1 &&
+    sed -e "s/line 1/changed line 1/" <file1 >file3 &&
+    mv file3 file1 &&
+    test_must_fail git reset --keep HEAD^ 2>err.log &&
+    grep file1 err.log | grep "not uptodate"
+'
+
 test_expect_success 'setup 3 different branches' '
     git reset --hard second &&
     git branch branch1 &&
@@ -156,6 +232,18 @@ test_expect_success '"reset --merge HEAD^" is ok with pending merge' '
 #
 #           working index HEAD target         working index HEAD
 #           ----------------------------------------------------
+# file1:     X       U     B    C     --keep   (disallowed)
+test_expect_success '"reset --keep HEAD^" fails with pending merge' '
+    git reset --hard third &&
+    test_must_fail git merge branch1 &&
+    test_must_fail git reset --keep HEAD^ 2>err.log &&
+    grep "middle of a merge" err.log
+'
+
+# The next test will test the following:
+#
+#           working index HEAD target         working index HEAD
+#           ----------------------------------------------------
 # file1:     X       U     B    B     --merge  B       B     B
 test_expect_success '"reset --merge HEAD" is ok with pending merge' '
     git reset --hard third &&
@@ -166,7 +254,19 @@ test_expect_success '"reset --merge HEAD" is ok with pending merge' '
     test -z "$(git diff)"
 '
 
-test_expect_success '--merge with added/deleted' '
+# The next test will test the following:
+#
+#           working index HEAD target         working index HEAD
+#           ----------------------------------------------------
+# file1:     X       U     B    B     --keep   (disallowed)
+test_expect_success '"reset --keep HEAD" fails with pending merge' '
+    git reset --hard third &&
+    test_must_fail git merge branch1 &&
+    test_must_fail git reset --keep HEAD 2>err.log &&
+    grep "middle of a merge" err.log
+'
+
+test_expect_success '--merge is ok with added/deleted merge' '
     git reset --hard third &&
     rm -f file2 &&
     test_must_fail git merge branch3 &&
@@ -180,4 +280,16 @@ test_expect_success '--merge with added/deleted' '
     git diff --exit-code --cached
 '
 
+test_expect_success '--keep fails with added/deleted merge' '
+    git reset --hard third &&
+    rm -f file2 &&
+    test_must_fail git merge branch3 &&
+    ! test -f file2 &&
+    test -f file3 &&
+    git diff --exit-code file3 &&
+    git diff --exit-code branch3 file3 &&
+    test_must_fail git reset --keep HEAD 2>err.log &&
+    grep "middle of a merge" err.log
+'
+
 test_done
diff --git a/t/t7111-reset-table.sh b/t/t7111-reset-table.sh
index de896c948d..ce421ad5ac 100755
--- a/t/t7111-reset-table.sh
+++ b/t/t7111-reset-table.sh
@@ -44,26 +44,32 @@ A B C D soft   A B D
 A B C D mixed  A D D
 A B C D hard   D D D
 A B C D merge  XXXXX
+A B C D keep   XXXXX
 A B C C soft   A B C
 A B C C mixed  A C C
 A B C C hard   C C C
 A B C C merge  XXXXX
+A B C C keep   A C C
 B B C D soft   B B D
 B B C D mixed  B D D
 B B C D hard   D D D
 B B C D merge  D D D
+B B C D keep   XXXXX
 B B C C soft   B B C
 B B C C mixed  B C C
 B B C C hard   C C C
 B B C C merge  C C C
+B B C C keep   B C C
 B C C D soft   B C D
 B C C D mixed  B D D
 B C C D hard   D D D
 B C C D merge  XXXXX
+B C C D keep   XXXXX
 B C C C soft   B C C
 B C C C mixed  B C C
 B C C C hard   C C C
 B C C C merge  B C C
+B C C C keep   B C C
 EOF
 
 test_expect_success 'setting up branches to test with unmerged entries' '
@@ -104,10 +110,12 @@ X U B C soft   XXXXX
 X U B C mixed  X C C
 X U B C hard   C C C
 X U B C merge  C C C
+X U B C keep   XXXXX
 X U B B soft   XXXXX
 X U B B mixed  X B B
 X U B B hard   B B B
 X U B B merge  B B B
+X U B B keep   XXXXX
 EOF
 
 test_done