[GSoC][PATCH v4 3/4] submodule: port set_name_rev() from shell to C

[Han-Wen Nienhuys <hanwen@google.com>]

LGTM with nits

commit message:

"revision name, and later handles its formating and printing."

typo: formatting

+		if (!capture_command(&cp, &sb, 0) && sb.len) {
+			strbuf_strip_suffix(&sb, "\n");
+			return strbuf_detach(&sb, NULL);
+		}

you discard all output if these commands fail, so if the argument is a
not a submodule, or the other is not a sha1, it will just print
nothing without error message. Maybe that is OK, though? I don't see
documentation for these commands, so maybe this is not meant to be
usable?