On 18/01/18 15:35, Johannes Schindelin wrote:
>
> This patch is part of the effort to reimplement `--preserve-merges` with
> a substantially improved design, a design that has been developed in the
> Git for Windows project to maintain the dozens of Windows-specific patch
> series on top of upstream Git.
>
> The previous patch implemented the `label`, `bud` and `reset` commands
> to label commits and to reset to a labeled commits. This patch adds the
> `merge` command, with the following syntax:
>
> merge <commit> <rev> <oneline>
I'm concerned that this will be confusing for users. All of the other
rebase commands replay the changes in the commit hash immediately
following the command name. This command instead uses the first commit
to specify the message which is different to both 'git merge' and the
existing rebase commands. I wonder if it would be clearer to have 'merge
-C <commit> <rev> ...' instead so it's clear which argument specifies
the message and which the remote head to merge. It would also allow for
'merge -c <commit> <rev> ...' in the future for rewording an existing
merge message and also avoid the slightly odd 'merge - <rev> ...'. Where
it's creating new merges I'm not sure it's a good idea to encourage
people to only have oneline commit messages by making it harder to edit
them, perhaps it could take another argument to mean open the editor or
not, though as Jake said I guess it's not that common.
One thought that just struck me - if a merge or reset command specifies
an invalid label is it rescheduled so that it's still in the to-do list
when the user edits it after rebase stops?
In the future it might be nice if the label, reset and merge commands
were validated when the to-do list is parsed so that the user gets
immediate feedback if they try to create a label that is not a valid ref
name or that they have a typo in a name given to reset or merge rather
than the rebase stopping later.
> The <commit> parameter in this instance is the *original* merge commit,
> whose author and message will be used for the to-be-created merge
> commit.
>
> The <rev> parameter refers to the (possibly rewritten) revision to
> merge. Let's see an example of a todo list:
>
> label onto
>
> # Branch abc
> bud
> pick deadbeef Hello, world!
> label abc
>
> bud
> pick cafecafe And now for something completely different
> merge baaabaaa abc Merge the branch 'abc' into master
>
> To support creating *new* merges, i.e. without copying the commit
> message from an existing commit, use the special value `-` as <commit>
> parameter (in which case the text after the <rev> parameter is used as
> commit message):
>
> merge - abc This will be the actual commit message of the merge
>
> This comes in handy when splitting a branch into two or more branches.
>
> Note: this patch only adds support for recursive merges, to keep things
> simple. Support for octopus merges will be added later in this patch
> series, support for merges using strategies other than the recursive
> merge is left for future contributions.
>
> The design of the `merge` command as introduced by this patch only
> supports creating new merge commits with exactly two parents, i.e. it
> adds no support for octopus merges.
>
> We will introduce support for octopus merges in a later commit.
>
> Signed-off-by: Johannes Schindelin <johannes.schinde...@gmx.de>
> ---
> git-rebase--interactive.sh | 1 +
> sequencer.c | 146
> +++++++++++++++++++++++++++++++++++++++++++--
> 2 files changed, 143 insertions(+), 4 deletions(-)
>
> diff --git a/git-rebase--interactive.sh b/git-rebase--interactive.sh
> index 3d2cd19d65a..5bf1ea3781f 100644
> --- a/git-rebase--interactive.sh
> +++ b/git-rebase--interactive.sh
> @@ -165,6 +165,7 @@ d, drop = remove commit
> l, label = label current HEAD with a name
> t, reset = reset HEAD to a label
> b, bud = reset HEAD to the revision labeled 'onto'
> +m, merge = create a merge commit using a given commit's message
>
> These lines can be re-ordered; they are executed from top to bottom.
> " | git stripspace --comment-lines >>"$todo"
> diff --git a/sequencer.c b/sequencer.c
> index 91cc55a002f..567cfcbbe8b 100644
> --- a/sequencer.c
> +++ b/sequencer.c
> @@ -779,6 +779,7 @@ enum todo_command {
> TODO_LABEL,
> TODO_RESET,
> TODO_BUD,
> + TODO_MERGE,
> /* commands that do nothing but are counted for reporting progress */
> TODO_NOOP,
> TODO_DROP,
> @@ -800,6 +801,7 @@ static struct {
> { 'l', "label" },
> { 't', "reset" },
> { 'b', "bud" },
> + { 'm', "merge" },
> { 0, "noop" },
> { 'd', "drop" },
> { 0, NULL }
> @@ -1304,14 +1306,20 @@ static int parse_insn_line(struct todo_item *item,
> const char *bol, char *eol)
> }
>
> end_of_object_name = (char *) bol + strcspn(bol, " \t\n");
> + item->arg = end_of_object_name + strspn(end_of_object_name, " \t");
> + item->arg_len = (int)(eol - item->arg);
> +
> saved = *end_of_object_name;
> + if (item->command == TODO_MERGE && *bol == '-' &&
> + bol + 1 == end_of_object_name) {
> + item->commit = NULL;
> + return 0;
> + }
> +
> *end_of_object_name = '\0';
> status = get_oid(bol, &commit_oid);
> *end_of_object_name = saved;
>
> - item->arg = end_of_object_name + strspn(end_of_object_name, " \t");
> - item->arg_len = (int)(eol - item->arg);
> -
> if (status < 0)
> return -1;
>
> @@ -2069,6 +2077,132 @@ static int do_reset(const char *name, int len)
> return ret;
> }
>
> +static int do_merge(struct commit *commit, const char *arg, int arg_len,
> + struct replay_opts *opts)
> +{
> + int merge_arg_len;
> + struct strbuf ref_name = STRBUF_INIT;
> + struct commit *head_commit, *merge_commit, *i;
> + struct commit_list *common, *j, *reversed = NULL;
> + struct merge_options o;
> + int ret;
> + static struct lock_file lock;
> +
> + for (merge_arg_len = 0; merge_arg_len < arg_len; merge_arg_len++)
> + if (isspace(arg[merge_arg_len]))
> + break;
> +
> + if (hold_locked_index(&lock, LOCK_REPORT_ON_ERROR) < 0)
> + return -1;
> +
> + if (commit) {
> + const char *message = get_commit_buffer(commit, NULL);
> + const char *body;
> + int len;
> +
> + if (!message) {
> + rollback_lock_file(&lock);
> + return error(_("could not get commit message of '%s'"),
> + oid_to_hex(&commit->object.oid));
> + }
> + write_author_script(message);
> + find_commit_subject(message, &body);
> + len = strlen(body);
> + if (write_message(body, len, git_path_merge_msg(), 0) < 0) {
> + error_errno(_("Could not write '%s'"),
> + git_path_merge_msg());
> + unuse_commit_buffer(commit, message);
> + rollback_lock_file(&lock);
> + return -1;
> + }
> + unuse_commit_buffer(commit, message);
> + } else {
> + const char *p = arg + merge_arg_len;
> + struct strbuf buf = STRBUF_INIT;
> + int len;
> +
> + strbuf_addf(&buf, "author %s", git_author_info(0));
> + write_author_script(buf.buf);
> + strbuf_reset(&buf);
> +
> + p += strspn(p, " \t");
> + if (*p)
> + len = strlen(p);
> + else {
> + strbuf_addf(&buf, "Merge branch '%.*s'",
> + merge_arg_len, arg);
> + p = buf.buf;
> + len = buf.len;
> + }
> +
> + if (write_message(p, len, git_path_merge_msg(), 0) < 0) {
> + error_errno(_("Could not write '%s'"),
> + git_path_merge_msg());
> + strbuf_release(&buf);
> + rollback_lock_file(&lock);
> + return -1;
> + }
> + strbuf_release(&buf);
> + }
> +
> + head_commit = lookup_commit_reference_by_name("HEAD");
> + if (!head_commit) {
> + rollback_lock_file(&lock);
> + return error(_("Cannot merge without a current revision"));
> + }
> +
> + strbuf_addf(&ref_name, "refs/rewritten/%.*s", merge_arg_len, arg);
> + merge_commit = lookup_commit_reference_by_name(ref_name.buf);
> + if (!merge_commit) {
> + /* fall back to non-rewritten ref or commit */
> + strbuf_splice(&ref_name, 0, strlen("refs/rewritten/"), "", 0);
> + merge_commit = lookup_commit_reference_by_name(ref_name.buf);
> + }
> + if (!merge_commit) {
> + error(_("could not resolve '%s'"), ref_name.buf);
> + strbuf_release(&ref_name);
> + rollback_lock_file(&lock);
> + return -1;
> + }
> + write_message(oid_to_hex(&merge_commit->object.oid), GIT_SHA1_HEXSZ,
> + git_path_merge_head(), 0);
> + write_message("no-ff", 5, git_path_merge_mode(), 0);
> +
> + common = get_merge_bases(head_commit, merge_commit);
> + for (j = common; j; j = j->next)
> + commit_list_insert(j->item, &reversed);
> + free_commit_list(common);
> +
> + read_cache();
> + init_merge_options(&o);
> + o.branch1 = "HEAD";
> + o.branch2 = ref_name.buf;
> + o.buffer_output = 2;
> +
> + ret = merge_recursive(&o, head_commit, merge_commit, reversed, &i);
> + if (ret <= 0)
> + fputs(o.obuf.buf, stdout);
> + strbuf_release(&o.obuf);
> + if (ret < 0) {
> + strbuf_release(&ref_name);
> + rollback_lock_file(&lock);
> + return error(_("conflicts while merging '%.*s'"),
> + merge_arg_len, arg);
> + }
> +
> + if (active_cache_changed &&
> + write_locked_index(&the_index, &lock, COMMIT_LOCK)) {
> + strbuf_release(&ref_name);
> + return error(_("merge: Unable to write new index file"));
> + }
> + rollback_lock_file(&lock);
> +
> + ret = run_git_commit(git_path_merge_msg(), opts, 0);
> + strbuf_release(&ref_name);
> +
> + return ret;
> +}
> +
> static int is_final_fixup(struct todo_list *todo_list)
> {
> int i = todo_list->current;
> @@ -2258,6 +2392,9 @@ static int pick_commits(struct todo_list *todo_list,
> struct replay_opts *opts)
> res = do_reset(item->arg, item->arg_len);
> else if (item->command == TODO_BUD)
> res = do_reset("onto", 4);
> + else if (item->command == TODO_MERGE)
> + res = do_merge(item->commit,
> + item->arg, item->arg_len, opts);
> else if (!is_noop(item->command))
> return error(_("unknown command %d"), item->command);
>
> @@ -2757,7 +2894,8 @@ int transform_todos(unsigned flags)
> oid_to_hex(&item->commit->object.oid);
>
> strbuf_addf(&buf, " %s", oid);
> - }
> + } else if (item->command == TODO_MERGE)
> + strbuf_addstr(&buf, " -");
> /* add all the rest */
> if (!item->arg_len)
> strbuf_addch(&buf, '\n');
>
