[PATH/RFC] parse-options: report invalid UTF-8 switches

[Erik Faye-Lund <kusmabite@gmail.com>]

Even though parse-options doesn't support UTF-8 switches (which
makes sense; non-ascii switches would be difficult to enter on
some keyboard layouts), it can be useful to report incorrectly
entered UTF-8 switches to make the output somewhat less ugly
for those of us with keyboard layouts with UTF-8 characters on
it.

Make the reporting code grok UTF-8 in the option sequence, and
write a variable-width output sequence.

Signed-off-by: Erik Faye-Lund <kusmabite@gmail.com>
---
As being both clumsy and Norwegian, I some times to enter the
Norwegian bizarro-letters ('æ', 'ø' and 'å') instead of the
correct ones when entering command-line options.

However, since git only looks at one byte at the time for
short-options, it ends up reporting a partial UTF-8 sequence
in such cases, leading to corruption of the output.

The "real fix" would probably be to add proper multi-byte
support to the short-option parser, but this serves little
purpose in Git; we don't internationalize the command-line
switches.

So perhaps this is a suitable band-aid instead?

 parse-options.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/parse-options.c b/parse-options.c
index 67e98a6..20dc742 100644
--- a/parse-options.c
+++ b/parse-options.c
@@ -3,6 +3,7 @@
 #include "cache.h"
 #include "commit.h"
 #include "color.h"
+#include "utf8.h"
 
 static int parse_options_usage(struct parse_opt_ctx_t *ctx,
 			       const char * const *usagestr,
@@ -462,7 +463,9 @@ int parse_options(int argc, const char **argv, const char *prefix,
 		if (ctx.argv[0][1] == '-') {
 			error("unknown option `%s'", ctx.argv[0] + 2);
 		} else {
-			error("unknown switch `%c'", *ctx.opt);
+			const char *next = ctx.opt;
+			utf8_width(&next, NULL);
+			error("unknown switch `%.*s'", (int)(next - ctx.opt), ctx.opt);
 		}
 		usage_with_options(usagestr, options);
 	}
-- 
1.7.11.7