sequencer (rebase -i): write an author-script file

When the interactive rebase aborts, it writes out an author-script file
to record the author information for the current commit. As we are about
to teach the sequencer how to perform the actions behind an interactive
rebase, it needs to write those author-script files, too.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

Author: dscho

sequencer.c

@@ -448,6 +448,52 @@ static int is_index_unchanged(void)
 	return !hashcmp(active_cache_tree->sha1, head_commit->tree->object.oid.hash);
 }
 
+static void write_author_script(const char *message)
+{
+	struct strbuf buf = STRBUF_INIT;
+	const char *eol;
+
+	for (;;)
+		if (!*message || starts_with(message, "\n")) {
+missing_author:
+			/* Missing 'author' line? */
+			unlink(author_script());
+			return;
+		}
+		else if (skip_prefix(message, "author ", &message))
+			break;
+		else if ((eol = strchr(message, '\n')))
+			message = eol + 1;
+		else
+			goto missing_author;
+
+	strbuf_addstr(&buf, "GIT_AUTHOR_NAME='");
+	while (*message && *message != '\n' && *message != '\r')
+		if (skip_prefix(message, " <", &message))
+			break;
+		else if (*message != '\'')
+			strbuf_addch(&buf, *(message++));
+		else
+			strbuf_addf(&buf, "'\\\\%c'", *(message++));
+	strbuf_addstr(&buf, "'\nGIT_AUTHOR_EMAIL='");
+	while (*message && *message != '\n' && *message != '\r')
+		if (skip_prefix(message, "> ", &message))
+			break;
+		else if (*message != '\'')
+			strbuf_addch(&buf, *(message++));
+		else
+			strbuf_addf(&buf, "'\\\\%c'", *(message++));
+	strbuf_addstr(&buf, "'\nGIT_AUTHOR_DATE='@");
+	while (*message && *message != '\n' && *message != '\r')
+		if (*message != '\'')
+			strbuf_addch(&buf, *(message++));
+		else
+			strbuf_addf(&buf, "'\\\\%c'", *(message++));
+	strbuf_addstr(&buf, "'\n");
+	write_file(author_script(), buf.buf);
+	strbuf_release(&buf);
+}
+
 static char **read_author_script()
 {
 	struct strbuf script = STRBUF_INIT;
@@ -894,6 +940,9 @@ static int do_pick_commit(enum todo_command command, struct commit *commit,
 		}
 	}
 
+	if (IS_REBASE_I())
+		write_author_script(msg.message);
+
 	if (!opts->strategy || !strcmp(opts->strategy, "recursive") || command == TODO_REVERT) {
 		res = do_recursive_merge(base, next, base_label, next_label,
 					 head, &msgbuf, opts);