rebase -i: introduce --recreate-merges=[no-]rebase-cousins

This one is a bit tricky to explain, so let's try with a diagram:

C
/   \
A - B - E - F
\   /
D

To illustrate what this new mode is all about, let's consider what
happens upon `git rebase -i --recreate-merges B`, in particular to
the commit `D`. So far, the new branch structure would be:

--- C' --
/         \
A - B ------ E' - F'
\    /
D'

This is not really preserving the branch topology from before! The
reason is that the commit `D` does not have `B` as ancestor, and
therefore it gets rebased onto `B`.

This is unintuitive behavior. Even worse, when recreating branch
structure, most use cases would appear to want cousins *not* to be
rebased onto the new base commit. For example, Git for Windows (the
heaviest user of the Git garden shears, which served as the blueprint
for --recreate-merges) frequently merges branches from `next` early, and
these branches certainly do *not* want to be rebased. In the example
above, the desired outcome would look like this:

--- C' --
/         \
A - B ------ E' - F'
\        /
-- D' --

Let's introduce the term "cousins" for such commits ("D" in the
example), and let's not rebase them by default, introducing the new
"rebase-cousins" mode for use cases where they should be rebased.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/Documentation/git-rebase.txt b/Documentation/git-rebase.txt
index e9da7e26329e89515a6794a6715bb5a9ab0397a1..0e6d020d92493e8033638d6de49fc6d32359d014 100644 (file)
--- a/Documentation/git-rebase.txt
+++ b/Documentation/git-rebase.txt
@@ -368,11 +368,16 @@ The commit list format can be changed by setting the configuration option
 rebase.instructionFormat.  A customized instruction format will automatically
 have the long commit hash prepended to the format.
 
---recreate-merges::
+--recreate-merges[=(rebase-cousins|no-rebase-cousins)]::
        Recreate merge commits instead of flattening the history by replaying
        merges. Merge conflict resolutions or manual amendments to merge
        commits are not recreated automatically, but have to be recreated
        manually.
++
+By default, or when `no-rebase-cousins` was specified, commits which do not
+have `<upstream>` as direct ancestor keep their original branch point.
+If the `rebase-cousins` mode is turned on, such commits are rebased onto
+`<upstream>` (or `<onto>`, if specified).
 
 -p::
 --preserve-merges::

diff --git a/builtin/rebase--helper.c b/builtin/rebase--helper.c
index a34ab5c06558e8233a6d19da3a13385cbe49b6df..cea99cb32354a6e19223c0a86a9ec319d838b0b2 100644 (file)
--- a/builtin/rebase--helper.c
+++ b/builtin/rebase--helper.c
@@ -13,7 +13,7 @@ int cmd_rebase__helper(int argc, const char **argv, const char *prefix)
 {
        struct replay_opts opts = REPLAY_OPTS_INIT;
        unsigned flags = 0, keep_empty = 0, recreate_merges = 0;
-       int abbreviate_commands = 0;
+       int abbreviate_commands = 0, rebase_cousins = -1;
        enum {
                CONTINUE = 1, ABORT, MAKE_SCRIPT, SHORTEN_OIDS, EXPAND_OIDS,
                CHECK_TODO_LIST, SKIP_UNNECESSARY_PICKS, REARRANGE_SQUASH,
@@ -23,6 +23,8 @@ int cmd_rebase__helper(int argc, const char **argv, const char *prefix)
                OPT_BOOL(0, "ff", &opts.allow_ff, N_("allow fast-forward")),
                OPT_BOOL(0, "keep-empty", &keep_empty, N_("keep empty commits")),
                OPT_BOOL(0, "recreate-merges", &recreate_merges, N_("recreate merge commits")),
+               OPT_BOOL(0, "rebase-cousins", &rebase_cousins,
+                        N_("keep original branch points of cousins")),
                OPT_CMDMODE(0, "continue", &command, N_("continue rebase"),
                                CONTINUE),
                OPT_CMDMODE(0, "abort", &command, N_("abort rebase"),
@@ -57,8 +59,13 @@ int cmd_rebase__helper(int argc, const char **argv, const char *prefix)
        flags |= keep_empty ? TODO_LIST_KEEP_EMPTY : 0;
        flags |= abbreviate_commands ? TODO_LIST_ABBREVIATE_CMDS : 0;
        flags |= recreate_merges ? TODO_LIST_RECREATE_MERGES : 0;
+       flags |= rebase_cousins > 0 ? TODO_LIST_REBASE_COUSINS : 0;
        flags |= command == SHORTEN_OIDS ? TODO_LIST_SHORTEN_IDS : 0;
 
+       if (rebase_cousins >= 0 && !recreate_merges)
+               warning(_("--[no-]rebase-cousins has no effect without "
+                         "--recreate-merges"));
+
        if (command == CONTINUE && argc == 1)
                return !!sequencer_continue(&opts);
        if (command == ABORT && argc == 1)

diff --git a/git-rebase--interactive.sh b/git-rebase--interactive.sh
index cfe3a537ac210a96919590e70c022fb263dd1ea2..e199fe1cca569fa03a7afc90c40342580169788c 100644 (file)
--- a/git-rebase--interactive.sh
+++ b/git-rebase--interactive.sh
@@ -903,6 +903,7 @@ if test t != "$preserve_merges"
 then
        git rebase--helper --make-script ${keep_empty:+--keep-empty} \
                ${recreate_merges:+--recreate-merges} \
+               ${rebase_cousins:+--rebase-cousins} \
                $revisions ${restrict_revision+^$restrict_revision} >"$todo" ||
        die "$(gettext "Could not generate todo list")"
 else

diff --git a/git-rebase.sh b/git-rebase.sh
index d69bc7d0e0d7847a30dbae8c84fbe3451c03e6de..58d778a2da05e3590d618417e2108dc05395321d 100755 (executable)
--- a/git-rebase.sh
+++ b/git-rebase.sh
@@ -17,7 +17,7 @@ q,quiet!           be quiet. implies --no-stat
 autostash          automatically stash/stash pop before and after
 fork-point         use 'merge-base --fork-point' to refine upstream
 onto=!             rebase onto given branch instead of upstream
-recreate-merges!   try to recreate merges instead of skipping them
+recreate-merges?   try to recreate merges instead of skipping them
 p,preserve-merges! try to recreate merges instead of ignoring them
 s,strategy=!       use the given merge strategy
 no-ff!             cherry-pick all commits, even if unchanged
@@ -88,6 +88,7 @@ state_dir=
 # One of {'', continue, skip, abort}, as parsed from command line
 action=
 recreate_merges=
+rebase_cousins=
 preserve_merges=
 autosquash=
 keep_empty=
@@ -268,6 +269,15 @@ do
                recreate_merges=t
                test -z "$interactive_rebase" && interactive_rebase=implied
                ;;
+       --recreate-merges=*)
+               recreate_merges=t
+               case "${1#*=}" in
+               rebase-cousins) rebase_cousins=t;;
+               no-rebase-cousins) rebase_cousins=;;
+               *) die "Unknown mode: $1";;
+               esac
+               test -z "$interactive_rebase" && interactive_rebase=implied
+               ;;
        --preserve-merges)
                preserve_merges=t
                test -z "$interactive_rebase" && interactive_rebase=implied

diff --git a/sequencer.c b/sequencer.c
index 0bb59e4411528a5cf3dee9b7d3db2c3514cb32c8..d8cc63dbe4da9553ae96b42f244c3c043bf56dc7 100644 (file)
--- a/sequencer.c
+++ b/sequencer.c
@@ -2937,6 +2937,7 @@ static int make_script_with_merges(struct pretty_print_context *pp,
                                   unsigned flags)
 {
        int keep_empty = flags & TODO_LIST_KEEP_EMPTY;
+       int rebase_cousins = flags & TODO_LIST_REBASE_COUSINS;
        struct strbuf buf = STRBUF_INIT, oneline = STRBUF_INIT;
        struct strbuf label = STRBUF_INIT;
        struct commit_list *commits = NULL, **tail = &commits, *iter;
@@ -3112,6 +3113,9 @@ static int make_script_with_merges(struct pretty_print_context *pp,
                                           &commit->object.oid);
                        if (entry)
                                to = entry->string;
+                       else if (!rebase_cousins)
+                               to = label_oid(&commit->object.oid, NULL,
+                                              &state);
 
                        if (!to || !strcmp(to, "onto"))
                                fprintf(out, "%s onto\n", cmd_reset);

diff --git a/sequencer.h b/sequencer.h
index 11d1ac925ef75e79f61f90db2920e9111d72ceda..deebc6e325823021a5cf02cf0d05b80bafe07655 100644 (file)
--- a/sequencer.h
+++ b/sequencer.h
@@ -49,6 +49,12 @@ int sequencer_remove_state(struct replay_opts *opts);
 #define TODO_LIST_SHORTEN_IDS (1U << 1)
 #define TODO_LIST_ABBREVIATE_CMDS (1U << 2)
 #define TODO_LIST_RECREATE_MERGES (1U << 3)
+/*
+ * When recreating merges, commits that do have the base commit as ancestor
+ * ("cousins") are *not* rebased onto the new base by default. If those
+ * commits should be rebased onto the new base, this flag needs to be passed.
+ */
+#define TODO_LIST_REBASE_COUSINS (1U << 4)
 int sequencer_make_script(FILE *out, int argc, const char **argv,
                          unsigned flags);
 

diff --git a/t/t3430-rebase-recreate-merges.sh b/t/t3430-rebase-recreate-merges.sh
index 2fb74cbbd32aa4ccf408c588c33ab7f39432e0fb..f2f44d2a66352b2145c863b3402aa7414ee6ba79 100755 (executable)
--- a/t/t3430-rebase-recreate-merges.sh
+++ b/t/t3430-rebase-recreate-merges.sh
@@ -143,6 +143,29 @@ test_expect_success 'with a branch tip that was cherry-picked already' '
        EOF
 '
 
+test_expect_success 'do not rebase cousins unless asked for' '
+       write_script copy-editor.sh <<-\EOF &&
+       cp "$1" "$(git rev-parse --git-path ORIGINAL-TODO)"
+       EOF
+
+       test_config sequence.editor \""$PWD"/copy-editor.sh\" &&
+       git checkout -b cousins master &&
+       before="$(git rev-parse --verify HEAD)" &&
+       test_tick &&
+       git rebase -i --recreate-merges HEAD^ &&
+       test_cmp_rev HEAD $before &&
+       test_tick &&
+       git rebase -i --recreate-merges=rebase-cousins HEAD^ &&
+       test_cmp_graph HEAD^.. <<-\EOF
+       *   Merge the topic branch '\''onebranch'\''
+       |\
+       | * D
+       | * G
+       |/
+       o H
+       EOF
+'
+
 test_expect_success 'refs/rewritten/* is worktree-local' '
        git worktree add wt &&
        cat >wt/script-from-scratch <<-\EOF &&