replace: add --graft option

The usage string for this option is:

git replace [-f] --graft <commit> [<parent>...]

First we create a new commit that is the same as <commit>
except that its parents are [<parents>...]

Then we create a replace ref that replace <commit> with
the commit we just created.

With this new option, it should be straightforward to
convert grafts to replace refs.

Signed-off-by: Christian Couder <chriscool@tuxfamily.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/builtin/replace.c b/builtin/replace.c
index 1bb491d3c4f282e7f68d25cae0e00f419df1dd93..74593596c67699720b87faee33a3790aa3117ee8 100644 (file)
--- a/builtin/replace.c
+++ b/builtin/replace.c
@@ -17,6 +17,7 @@
 static const char * const git_replace_usage[] = {
        N_("git replace [-f] <object> <replacement>"),
        N_("git replace [-f] --edit <object>"),
 static const char * const git_replace_usage[] = {
        N_("git replace [-f] <object> <replacement>"),
        N_("git replace [-f] --edit <object>"),

+       N_("git replace [-f] --graft <commit> [<parent>...]"),

        N_("git replace -d <object>..."),
        N_("git replace [--format=<format>] [-l [<pattern>]]"),
        NULL
        N_("git replace -d <object>..."),
        N_("git replace [--format=<format>] [-l [<pattern>]]"),
        NULL


@@ -294,6 +295,66 @@ static int edit_and_replace(const char *object_ref, int force)
        return replace_object_sha1(object_ref, old, "replacement", new, force);
 }
 
        return replace_object_sha1(object_ref, old, "replacement", new, force);
 }
 

+static void replace_parents(struct strbuf *buf, int argc, const char **argv)
+{
+       struct strbuf new_parents = STRBUF_INIT;
+       const char *parent_start, *parent_end;
+       int i;
+
+       /* find existing parents */
+       parent_start = buf->buf;
+       parent_start += 46; /* "tree " + "hex sha1" + "\n" */
+       parent_end = parent_start;
+
+       while (starts_with(parent_end, "parent "))
+               parent_end += 48; /* "parent " + "hex sha1" + "\n" */
+
+       /* prepare new parents */
+       for (i = 0; i < argc; i++) {
+               unsigned char sha1[20];
+               if (get_sha1(argv[i], sha1) < 0)
+                       die(_("Not a valid object name: '%s'"), argv[i]);
+               lookup_commit_or_die(sha1, argv[i]);
+               strbuf_addf(&new_parents, "parent %s\n", sha1_to_hex(sha1));
+       }
+
+       /* replace existing parents with new ones */
+       strbuf_splice(buf, parent_start - buf->buf, parent_end - parent_start,
+                     new_parents.buf, new_parents.len);
+
+       strbuf_release(&new_parents);
+}
+
+static int create_graft(int argc, const char **argv, int force)
+{
+       unsigned char old[20], new[20];
+       const char *old_ref = argv[0];
+       struct commit *commit;
+       struct strbuf buf = STRBUF_INIT;
+       const char *buffer;
+       unsigned long size;
+
+       if (get_sha1(old_ref, old) < 0)
+               die(_("Not a valid object name: '%s'"), old_ref);
+       commit = lookup_commit_or_die(old, old_ref);
+
+       buffer = get_commit_buffer(commit, &size);
+       strbuf_add(&buf, buffer, size);
+       unuse_commit_buffer(commit, buffer);
+
+       replace_parents(&buf, argc - 1, &argv[1]);
+
+       if (write_sha1_file(buf.buf, buf.len, commit_type, new))
+               die(_("could not write replacement commit for: '%s'"), old_ref);
+
+       strbuf_release(&buf);
+
+       if (!hashcmp(old, new))
+               return error("new commit is the same as the old one: '%s'", sha1_to_hex(old));
+
+       return replace_object_sha1(old_ref, old, "replacement", new, force);
+}
+

 int cmd_replace(int argc, const char **argv, const char *prefix)
 {
        int force = 0;
 int cmd_replace(int argc, const char **argv, const char *prefix)
 {
        int force = 0;


@@ -303,12 +364,14 @@ int cmd_replace(int argc, const char **argv, const char *prefix)
                MODE_LIST,
                MODE_DELETE,
                MODE_EDIT,
                MODE_LIST,
                MODE_DELETE,
                MODE_EDIT,

+               MODE_GRAFT,

                MODE_REPLACE
        } cmdmode = MODE_UNSPECIFIED;
        struct option options[] = {
                OPT_CMDMODE('l', "list", &cmdmode, N_("list replace refs"), MODE_LIST),
                OPT_CMDMODE('d', "delete", &cmdmode, N_("delete replace refs"), MODE_DELETE),
                OPT_CMDMODE('e', "edit", &cmdmode, N_("edit existing object"), MODE_EDIT),
                MODE_REPLACE
        } cmdmode = MODE_UNSPECIFIED;
        struct option options[] = {
                OPT_CMDMODE('l', "list", &cmdmode, N_("list replace refs"), MODE_LIST),
                OPT_CMDMODE('d', "delete", &cmdmode, N_("delete replace refs"), MODE_DELETE),
                OPT_CMDMODE('e', "edit", &cmdmode, N_("edit existing object"), MODE_EDIT),

+               OPT_CMDMODE('g', "graft", &cmdmode, N_("change a commit's parents"), MODE_GRAFT),

                OPT_BOOL('f', "force", &force, N_("replace the ref if it exists")),
                OPT_STRING(0, "format", &format, N_("format"), N_("use this format")),
                OPT_END()
                OPT_BOOL('f', "force", &force, N_("replace the ref if it exists")),
                OPT_STRING(0, "format", &format, N_("format"), N_("use this format")),
                OPT_END()


@@ -325,7 +388,10 @@ int cmd_replace(int argc, const char **argv, const char *prefix)
                usage_msg_opt("--format cannot be used when not listing",
                              git_replace_usage, options);
 
                usage_msg_opt("--format cannot be used when not listing",
                              git_replace_usage, options);
 

-       if (force && cmdmode != MODE_REPLACE && cmdmode != MODE_EDIT)
+       if (force &&
+           cmdmode != MODE_REPLACE &&
+           cmdmode != MODE_EDIT &&
+           cmdmode != MODE_GRAFT)

                usage_msg_opt("-f only makes sense when writing a replacement",
                              git_replace_usage, options);
 
                usage_msg_opt("-f only makes sense when writing a replacement",
                              git_replace_usage, options);
 


@@ -348,6 +414,12 @@ int cmd_replace(int argc, const char **argv, const char *prefix)
                                      git_replace_usage, options);
                return edit_and_replace(argv[0], force);
 
                                      git_replace_usage, options);
                return edit_and_replace(argv[0], force);
 

+       case MODE_GRAFT:
+               if (argc < 1)
+                       usage_msg_opt("-g needs at least one argument",
+                                     git_replace_usage, options);
+               return create_graft(argc, argv, force);
+

        case MODE_LIST:
                if (argc > 1)
                        usage_msg_opt("only one pattern can be given with -l",
        case MODE_LIST:
                if (argc > 1)
                        usage_msg_opt("only one pattern can be given with -l",