Re: *Really* noisy encoding warnings post-v2.33.0

[Jeff King <peff@peff.net>]

On Fri, Oct 08, 2021 at 10:36:02PM -0400, Jeff King wrote:

> If that were coupled with, say, an advise() call to explain that output
> and matching might be inaccurate (and show that _once_), that might
> might it more clear what's going on.
> 
> Now I am sympathetic to flooding the user with too many messages, and
> maybe reducing this to a single instance of "some commit messages could
> not be re-encoded; output and matching might be inaccurate" is the right
> thing. But in a sense, it's also working as designed: what you asked for
> is producing wrong output over and over, and Git is saying so.

The single-output version would perhaps be something like this:

diff --git a/pretty.c b/pretty.c
index 708b618cfe..c86f41bae7 100644
--- a/pretty.c
+++ b/pretty.c
@@ -606,6 +606,21 @@ static char *replace_encoding_header(char *buf, const char *encoding)
 	return strbuf_detach(&tmp, NULL);
 }
 
+static void show_encoding_warning(const char *output_encoding)
+{
+	static int seen_warning;
+
+	if (seen_warning)
+		return;
+
+	seen_warning = 1;
+	warning("one or more commits could not be re-encoded to '%s'",
+		output_encoding);
+	advise("When re-encoding fails, some output may be in an unexpected\n"
+	       "encoding, and pattern matches against commit data may be\n"
+	       "inaccurate.");
+}
+
 const char *repo_logmsg_reencode(struct repository *r,
 				 const struct commit *commit,
 				 char **commit_encoding,
@@ -673,7 +688,7 @@ const char *repo_logmsg_reencode(struct repository *r,
 	 * case we just return the commit message verbatim.
 	 */
 	if (!out) {
-		warning("unable to reencode commit to '%s'", output_encoding);
+		show_encoding_warning(output_encoding);
 		return msg;
 	}
 	return out;