+/**
+ * Reads a KEY=VALUE shell variable assignment from `fp`, returning the VALUE
+ * as a newly-allocated string. VALUE must be a quoted string, and the KEY must
+ * match `key`. Returns NULL on failure.
+ *
+ * This is used by read_author_script() to read the GIT_AUTHOR_* variables from
+ * the author-script.
+ */
+static char *read_shell_var(FILE *fp, const char *key)
+{
+ struct strbuf sb = STRBUF_INIT;
+ const char *str;
+
+ if (strbuf_getline(&sb, fp, '\n'))
+ goto fail;
+
+ if (!skip_prefix(sb.buf, key, &str))
+ goto fail;
+
+ if (!skip_prefix(str, "=", &str))
+ goto fail;
+
+ strbuf_remove(&sb, 0, str - sb.buf);
+
+ str = sq_dequote(sb.buf);
+ if (!str)
+ goto fail;
+
+ return strbuf_detach(&sb, NULL);
+
+fail:
+ strbuf_release(&sb);
+ return NULL;
+}
+
+/**
+ * Reads and parses the state directory's "author-script" file, and sets
+ * state->author_name, state->author_email and state->author_date accordingly.
+ * Returns 0 on success, -1 if the file could not be parsed.
+ *
+ * The author script is of the format:
+ *
+ * GIT_AUTHOR_NAME='$author_name'
+ * GIT_AUTHOR_EMAIL='$author_email'
+ * GIT_AUTHOR_DATE='$author_date'
+ *
+ * where $author_name, $author_email and $author_date are quoted. We are strict
+ * with our parsing, as the file was meant to be eval'd in the old git-am.sh
+ * script, and thus if the file differs from what this function expects, it is
+ * better to bail out than to do something that the user does not expect.
+ */
+static int read_author_script(struct am_state *state)
+{
+ const char *filename = am_path(state, "author-script");
+ FILE *fp;
+
+ assert(!state->author_name);
+ assert(!state->author_email);
+ assert(!state->author_date);
+
+ fp = fopen(filename, "r");
+ if (!fp) {
+ if (errno == ENOENT)
+ return 0;
+ die_errno(_("could not open '%s' for reading"), filename);
+ }
+
+ state->author_name = read_shell_var(fp, "GIT_AUTHOR_NAME");
+ if (!state->author_name) {
+ fclose(fp);
+ return -1;
+ }
+
+ state->author_email = read_shell_var(fp, "GIT_AUTHOR_EMAIL");
+ if (!state->author_email) {
+ fclose(fp);
+ return -1;
+ }
+
+ state->author_date = read_shell_var(fp, "GIT_AUTHOR_DATE");
+ if (!state->author_date) {
+ fclose(fp);
+ return -1;
+ }
+
+ if (fgetc(fp) != EOF) {
+ fclose(fp);
+ return -1;
+ }
+
+ fclose(fp);
+ return 0;
+}
+
+/**
+ * Saves state->author_name, state->author_email and state->author_date in the
+ * state directory's "author-script" file.
+ */
+static void write_author_script(const struct am_state *state)
+{
+ struct strbuf sb = STRBUF_INIT;
+
+ strbuf_addstr(&sb, "GIT_AUTHOR_NAME=");
+ sq_quote_buf(&sb, state->author_name);
+ strbuf_addch(&sb, '\n');
+
+ strbuf_addstr(&sb, "GIT_AUTHOR_EMAIL=");
+ sq_quote_buf(&sb, state->author_email);
+ strbuf_addch(&sb, '\n');
+
+ strbuf_addstr(&sb, "GIT_AUTHOR_DATE=");
+ sq_quote_buf(&sb, state->author_date);
+ strbuf_addch(&sb, '\n');
+
+ write_file(am_path(state, "author-script"), 1, "%s", sb.buf);
+
+ strbuf_release(&sb);
+}
+
+/**
+ * Reads the commit message from the state directory's "final-commit" file,
+ * setting state->msg to its contents and state->msg_len to the length of its
+ * contents in bytes.
+ *
+ * Returns 0 on success, -1 if the file does not exist.
+ */
+static int read_commit_msg(struct am_state *state)
+{
+ struct strbuf sb = STRBUF_INIT;
+
+ assert(!state->msg);
+
+ if (read_state_file(&sb, state, "final-commit", 0) < 0) {
+ strbuf_release(&sb);
+ return -1;
+ }
+
+ state->msg = strbuf_detach(&sb, &state->msg_len);
+ return 0;
+}
+
+/**
+ * Saves state->msg in the state directory's "final-commit" file.
+ */
+static void write_commit_msg(const struct am_state *state)
+{
+ int fd;
+ const char *filename = am_path(state, "final-commit");
+
+ fd = xopen(filename, O_WRONLY | O_CREAT, 0666);
+ if (write_in_full(fd, state->msg, state->msg_len) < 0)
+ die_errno(_("could not write to %s"), filename);
+ close(fd);
+}
+