diff: add flag to indicate textconv was set via cmdline

git-show is unique in that it wants to use textconv by default except
for when it is showing blobs.  When asked to show a blob, show doesn't
want to use textconv unless the user explicitly requested that it be
used by providing the command line flag '--textconv'.

Currently this is done by using a parallel set of 'touched' flags which
get set every time a particular flag is set or cleared.  In a future
patch we want to eliminate this parallel set of flags so instead of
relying on if the textconv flag has been touched, add a new flag
'TEXTCONV_SET_VIA_CMDLINE' which is only set if textconv is set to true
via the command line.

Signed-off-by: Brandon Williams <bmwill@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/log.c

@@ -485,7 +485,7 @@ static int show_blob_object(const struct object_id *oid, struct rev_info *rev, c
 	unsigned long size;
 
 	fflush(rev->diffopt.file);
-	if (!DIFF_OPT_TOUCHED(&rev->diffopt, ALLOW_TEXTCONV) ||
+	if (!DIFF_OPT_TST(&rev->diffopt, TEXTCONV_SET_VIA_CMDLINE) ||
 	    !DIFF_OPT_TST(&rev->diffopt, ALLOW_TEXTCONV))
 		return stream_blob_to_fd(1, oid, NULL, 0);
 

diff.c

@@ -4762,9 +4762,10 @@ int diff_opt_parse(struct diff_options *options,
 		DIFF_OPT_SET(options, ALLOW_EXTERNAL);
 	else if (!strcmp(arg, "--no-ext-diff"))
 		DIFF_OPT_CLR(options, ALLOW_EXTERNAL);
-	else if (!strcmp(arg, "--textconv"))
+	else if (!strcmp(arg, "--textconv")) {
 		DIFF_OPT_SET(options, ALLOW_TEXTCONV);
-	else if (!strcmp(arg, "--no-textconv"))
+		DIFF_OPT_SET(options, TEXTCONV_SET_VIA_CMDLINE);
+	} else if (!strcmp(arg, "--no-textconv"))
 		DIFF_OPT_CLR(options, ALLOW_TEXTCONV);
 	else if (!strcmp(arg, "--ignore-submodules")) {
 		DIFF_OPT_SET(options, OVERRIDE_SUBMODULE_CONFIG);

diff.h

@@ -83,6 +83,7 @@ struct diff_flags {
 	unsigned DIRSTAT_CUMULATIVE:1;
 	unsigned DIRSTAT_BY_FILE:1;
 	unsigned ALLOW_TEXTCONV:1;
+	unsigned TEXTCONV_SET_VIA_CMDLINE:1;
 	unsigned DIFF_FROM_CONTENTS:1;
 	unsigned DIRTY_SUBMODULES:1;
 	unsigned IGNORE_UNTRACKED_IN_SUBMODULES:1;