Re: [PATCH v3 2/4] revision.h: refactor "disable_stdin" and "read_from_stdin"

Ævar Arnfjörð Bjarmason  [off-list ref] writes:

Change the two "disable_stdin" and "read_from_stdin" flags to an enum,
in preparation for a subsequent commit adding more flags.

The interaction between these is more subtle than they might appear at
first sight, as noted in a12cbe23ef7. "read_stdin" is not the inverse
of "disable_stdin", rather we read stdin if we see the "--stdin"
option.

The "read" is intended to understood as "I read it", not "you should

"I've read it already" would have been easier to understand.

 			if (!strcmp(arg, "--stdin")) {
-				if (revs->disable_stdin) {
+				switch (revs->stdin_handling) {
+				case REV_INFO_STDIN_IGNORE:
 					argv[left++] = arg;
 					continue;
+				case REV_INFO_STDIN_CONSUME_ON_OPTION:
+					if (revs->consumed_stdin++)
+						die("--stdin given twice?");
+					read_revisions_from_stdin(revs, &prune_data);
+					continue;
 				}

More importantly, consumed_stdin will start at zero and if it is
found to be non-zero here, it is an immediate error, hence ...

+	/*
+	 * Did we read from stdin due to stdin_handling ==
+	 * REV_INFO_STDIN_CONSUME_ON_OPTION and seeing the --stdin
+	 * option?
 	 */
-	int read_from_stdin;
+	int consumed_stdin;

... it does not have to be a full integer.
Just a single-bit would do.

But none of the above is grave enough to require an update.