help: reuse print_columns() for help -a

diff --git a/builtin/merge.c b/builtin/merge.c
index f385b8ac9e759f74b4711bdb93687202c1bc1600..d3e1e8dc9e478aaea7ef4da855fb7c2e10397644 100644 (file)
--- a/builtin/merge.c
+++ b/builtin/merge.c
@@ -885,20 +885,30 @@ static void abort_commit(const char *err_msg)
        exit(1);
 }
 
+static const char merge_editor_comment[] =
+N_("Please enter a commit message to explain why this merge is necessary,\n"
+   "especially if it merges an updated upstream into a topic branch.\n"
+   "\n"
+   "Lines starting with '#' will be ignored, and an empty message aborts\n"
+   "the commit.\n");
+
 static void prepare_to_commit(void)
 {
        struct strbuf msg = STRBUF_INIT;
+       const char *comment = _(merge_editor_comment);
        strbuf_addbuf(&msg, &merge_msg);
        strbuf_addch(&msg, '\n');
+       if (0 < option_edit)
+               strbuf_add_lines(&msg, "# ", comment, strlen(comment));
        write_merge_msg(&msg);
        run_hook(get_index_file(), "prepare-commit-msg",
                 git_path("MERGE_MSG"), "merge", NULL, NULL);
-       if (option_edit) {
+       if (0 < option_edit) {
                if (launch_editor(git_path("MERGE_MSG"), NULL, NULL))
                        abort_commit(NULL);
        }
        read_merge_msg(&msg);
-       stripspace(&msg, option_edit);
+       stripspace(&msg, 0 < option_edit);
        if (!msg.len)
                abort_commit(_("Empty commit message."));
        strbuf_release(&merge_msg);
@@ -1099,6 +1109,33 @@ static void write_merge_state(void)
        close(fd);
 }
 
+static int default_edit_option(void)
+{
+       static const char name[] = "GIT_MERGE_AUTOEDIT";
+       const char *e = getenv(name);
+       struct stat st_stdin, st_stdout;
+
+       if (have_message)
+               /* an explicit -m msg without --[no-]edit */
+               return 0;
+
+       if (e) {
+               int v = git_config_maybe_bool(name, e);
+               if (v < 0)
+                       die("Bad value '%s' in environment '%s'", e, name);
+               return v;
+       }
+
+       /* Use editor if stdin and stdout are the same and is a tty */
+       return (!fstat(0, &st_stdin) &&
+               !fstat(1, &st_stdout) &&
+               isatty(0) && isatty(1) &&
+               st_stdin.st_dev == st_stdout.st_dev &&
+               st_stdin.st_ino == st_stdout.st_ino &&
+               st_stdin.st_mode == st_stdout.st_mode);
+}
+
+
 int cmd_merge(int argc, const char **argv, const char *prefix)
 {
        unsigned char result_tree[20];
@@ -1294,7 +1331,7 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
        }
 
        if (option_edit < 0)
-               option_edit = 0;
+               option_edit = default_edit_option();
 
        if (!use_strategies) {
                if (!remoteheads->next)