Re: [PATCH 2/6] diff-merges: move specific diff-index "-m" handling to diff-index

Junio C Hamano [off-list ref] writes:

Sergey Organov [off-list ref] writes:

quoted

 int cmd_diff_index(int argc, const char **argv, const char *prefix)
 {
 	struct rev_info rev;
 	unsigned int option = 0;
-	int i;
 	int result;
 
 	if (argc == 2 && !strcmp(argv[1], "-h"))

@@ -27,17 +53,16 @@ int cmd_diff_index(int argc, const char **argv, const char *prefix)
 	rev.abbrev = 0;
 	prefix = precompose_argv_prefix(argc, argv, prefix);
 
+	/*
+	 * It's essential to parse our distinct options before calling
+	 * setup_revisions(), for the latter not to see "-m".
+	 */
+	argc = parse_distinct_options(argc, argv, &rev, &option);
 	argc = setup_revisions(argc, argv, &rev, NULL);

This change is risky, as the loop below (which this patch moves to
parse_distinct_options()) has no knowledge of other options that
setup_revisions() helper is prepared to handle and that takes an
argument.  When parsing "git cmd --opt --cached A", setup_revisions()
may know that --opt takes an argument and eat both (i.e. the
"--cached" is not an option but an arg given to "--opt"), but the
new parse_distinct_options() helper does not; it will happily skip
"--opt" and leave it in, mistake "--cached" as an option and remove,
and instead make "A" the arg given to "--opt".

Picking up the remnant _after_ setup_revisions() ate what it
understands would not have such a downside, as long as none of our
"distinct options" take any argument.

Can't we make "-m means something special for diff-index" without
butchering the command line processing in this step?  diff-index
does not care about --diff-merges, so letting setup_revisions()
remember only the fact that "-m" was given while parsing, and then
postprocess what "-m" means depending on the command (i.e. everybody
else would treat it as a short-hand for "--diff-merges=m" plus "we
need some form of diff output, while allowing "diff-index" to treat
it differently) should not be rocket science.

I have already considered a few ways of doing it, and what I came up
with looked least destructive to me at the moment, especially as it
broke no tests whatsoever.

I'll now re-consider my approach because of your observations, thanks!

-- Sergey Organov