format-patch: use branch description in cover letter

Use the description for the branch when preparing the cover letter
when available.

While at it, mark a loosely written codepath that would do a random and
useless thing given an unusual input (e.g. "^master HEAD HEAD^"), which
we may want to fix someday.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/builtin/log.c b/builtin/log.c
index f5d49305903911eb7aa0fb3f73e0fd950b896228..e80a925b7b521415b92851222e6a869620a1ff22 100644 (file)
--- a/builtin/log.c
+++ b/builtin/log.c
@@ -19,6 +19,7 @@
 #include "remote.h"
 #include "string-list.h"
 #include "parse-options.h"
+#include "branch.h"
 
 /* Set a default date-time format for git log ("log.date" config variable) */
 static const char *default_date_mode = NULL;
@@ -746,10 +747,24 @@ static void print_signature(void)
                printf("-- \n%s\n\n", signature);
 }
 
+static void add_branch_description(struct strbuf *buf, const char *branch_name)
+{
+       struct strbuf desc = STRBUF_INIT;
+       if (!branch_name || !*branch_name)
+               return;
+       read_branch_desc(&desc, branch_name);
+       if (desc.len) {
+               strbuf_addch(buf, '\n');
+               strbuf_add(buf, desc.buf, desc.len);
+               strbuf_addch(buf, '\n');
+       }
+}
+
 static void make_cover_letter(struct rev_info *rev, int use_stdout,
                              int numbered, int numbered_files,
                              struct commit *origin,
                              int nr, struct commit **list, struct commit *head,
+                             const char *branch_name,
                              int quiet)
 {
        const char *committer;
@@ -807,6 +822,7 @@ static void make_cover_letter(struct rev_info *rev, int use_stdout,
        pp_user_info(&pp, NULL, &sb, committer, encoding);
        pp_title_line(&pp, &msg, &sb, encoding, need_8bit_cte);
        pp_remainder(&pp, &msg, &sb, 0);
+       add_branch_description(&sb, branch_name);
        printf("%s\n", sb.buf);
 
        strbuf_release(&sb);
@@ -1006,6 +1022,35 @@ static int cc_callback(const struct option *opt, const char *arg, int unset)
        return 0;
 }
 
+static char *find_branch_name(struct rev_info *rev)
+{
+       int i, positive = -1;
+       unsigned char branch_sha1[20];
+       struct strbuf buf = STRBUF_INIT;
+       const char *branch;
+
+       for (i = 0; i < rev->cmdline.nr; i++) {
+               if (rev->cmdline.rev[i].flags & UNINTERESTING)
+                       continue;
+               if (positive < 0)
+                       positive = i;
+               else
+                       return NULL;
+       }
+       if (positive < 0)
+               return NULL;
+       strbuf_addf(&buf, "refs/heads/%s", rev->cmdline.rev[positive].name);
+       branch = resolve_ref(buf.buf, branch_sha1, 1, 0);
+       if (!branch ||
+           prefixcmp(branch, "refs/heads/") ||
+           hashcmp(rev->cmdline.rev[positive].item->sha1, branch_sha1))
+               branch = NULL;
+       strbuf_release(&buf);
+       if (branch)
+               return xstrdup(rev->cmdline.rev[positive].name);
+       return NULL;
+}
+
 int cmd_format_patch(int argc, const char **argv, const char *prefix)
 {
        struct commit *commit;
@@ -1027,6 +1072,7 @@ int cmd_format_patch(int argc, const char **argv, const char *prefix)
        struct strbuf buf = STRBUF_INIT;
        int use_patch_format = 0;
        int quiet = 0;
+       char *branch_name = NULL;
        const struct option builtin_format_patch_options[] = {
                { OPTION_CALLBACK, 'n', "numbered", &numbered, NULL,
                            "use [PATCH n/m] even with a single patch",
@@ -1217,8 +1263,16 @@ int cmd_format_patch(int argc, const char **argv, const char *prefix)
                         * origin" that prepares what the origin side still
                         * does not have.
                         */
+                       unsigned char sha1[20];
+                       const char *ref;
+
                        rev.pending.objects[0].item->flags |= UNINTERESTING;
                        add_head_to_pending(&rev);
+                       ref = resolve_ref("HEAD", sha1, 1, NULL);
+                       if (ref && !prefixcmp(ref, "refs/heads/"))
+                               branch_name = xstrdup(ref + strlen("refs/heads/"));
+                       else
+                               branch_name = xstrdup(""); /* no branch */
                }
                /*
                 * Otherwise, it is "format-patch -22 HEAD", and/or
@@ -1234,16 +1288,26 @@ int cmd_format_patch(int argc, const char **argv, const char *prefix)
        rev.show_root_diff = 1;
 
        if (cover_letter) {
-               /* remember the range */
+               /*
+                * NEEDSWORK:randomly pick one positive commit to show
+                * diffstat; this is often the tip and the command
+                * happens to do the right thing in most cases, but a
+                * complex command like "--cover-letter a b c ^bottom"
+                * picks "c" and shows diffstat between bottom..c
+                * which may not match what the series represents at
+                * all and totally broken.
+                */
                int i;
                for (i = 0; i < rev.pending.nr; i++) {
                        struct object *o = rev.pending.objects[i].item;
                        if (!(o->flags & UNINTERESTING))
                                head = (struct commit *)o;
                }
-               /* We can't generate a cover letter without any patches */
+               /* There is nothing to show; it is not an error, though. */
                if (!head)
                        return 0;
+               if (!branch_name)
+                       branch_name = find_branch_name(&rev);
        }
 
        if (ignore_if_in_upstream) {
@@ -1294,7 +1358,7 @@ int cmd_format_patch(int argc, const char **argv, const char *prefix)
                if (thread)
                        gen_message_id(&rev, "cover");
                make_cover_letter(&rev, use_stdout, numbered, numbered_files,
-                                 origin, nr, list, head, quiet);
+                                 origin, nr, list, head, branch_name, quiet);
                total++;
                start_number--;
        }
@@ -1366,6 +1430,7 @@ int cmd_format_patch(int argc, const char **argv, const char *prefix)
                        fclose(stdout);
        }
        free(list);
+       free(branch_name);
        string_list_clear(&extra_to, 0);
        string_list_clear(&extra_cc, 0);
        string_list_clear(&extra_hdr, 0);