format-patch: allow additional generated content in make_cover_letter()

make_cover_letter() returns early when it lacks sufficient state to emit
a diffstat, which makes it difficult to extend the function to reliably
emit additional generated content. Work around this shortcoming by
factoring diffstat-printing logic out to its own function and calling it
as needed without otherwise inhibiting normal control flow.

Signed-off-by: Eric Sunshine <sunshine@sunshineco.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/builtin/log.c b/builtin/log.c
index 805f89d7e1552e86a8c2b990a0e213d09f91d42a..873aabcf40fb123bee28bd6119e1bd0895941e37 100644 (file)
--- a/builtin/log.c
+++ b/builtin/log.c
@@ -997,6 +997,26 @@ static char *find_branch_name(struct rev_info *rev)
        return branch;
 }
 
+static void show_diffstat(struct rev_info *rev,
+                         struct commit *origin, struct commit *head)
+{
+       struct diff_options opts;
+
+       memcpy(&opts, &rev->diffopt, sizeof(opts));
+       opts.output_format = DIFF_FORMAT_SUMMARY | DIFF_FORMAT_DIFFSTAT;
+       opts.stat_width = MAIL_DEFAULT_WRAP;
+
+       diff_setup_done(&opts);
+
+       diff_tree_oid(get_commit_tree_oid(origin),
+                     get_commit_tree_oid(head),
+                     "", &opts);
+       diffcore_std(&opts);
+       diff_flush(&opts);
+
+       fprintf(rev->diffopt.file, "\n");
+}
+
 static void make_cover_letter(struct rev_info *rev, int use_stdout,
                              struct commit *origin,
                              int nr, struct commit **list,
@@ -1010,7 +1030,6 @@ static void make_cover_letter(struct rev_info *rev, int use_stdout,
        struct strbuf sb = STRBUF_INIT;
        int i;
        const char *encoding = "UTF-8";
-       struct diff_options opts;
        int need_8bit_cte = 0;
        struct pretty_print_context pp = {0};
        struct commit *head = list[0];
@@ -1060,25 +1079,9 @@ static void make_cover_letter(struct rev_info *rev, int use_stdout,
 
        shortlog_output(&log);
 
-       /*
-        * We can only do diffstat with a unique reference point
-        */
-       if (!origin)
-               return;
-
-       memcpy(&opts, &rev->diffopt, sizeof(opts));
-       opts.output_format = DIFF_FORMAT_SUMMARY | DIFF_FORMAT_DIFFSTAT;
-       opts.stat_width = MAIL_DEFAULT_WRAP;
-
-       diff_setup_done(&opts);
-
-       diff_tree_oid(get_commit_tree_oid(origin),
-                     get_commit_tree_oid(head),
-                     "", &opts);
-       diffcore_std(&opts);
-       diff_flush(&opts);
-
-       fprintf(rev->diffopt.file, "\n");
+       /* We can only do diffstat with a unique reference point */
+       if (origin)
+               show_diffstat(rev, origin, head);
 }
 
 static const char *clean_message_id(const char *msg_id)