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git/diff-merges.c
Jonathan Nieder 6a38e33331 Revert 'diff-merges: let "-m" imply "-p"' 
This reverts commit f5bfcc823b, which
made "git log -m" imply "--patch" by default.  The logic was that
"-m", which makes diff generation for merges perform a diff against
each parent, has no use unless I am viewing the diff, so we could save
the user some typing by turning on display of the resulting diff
automatically.  That wasn't expected to adversely affect scripts
because scripts would either be using a command like "git diff-tree"
that already emits diffs by default or would be combining -m with a
diff generation option such as --name-status.  By saving typing for
interactive use without adversely affecting scripts in the wild, it
would be a pure improvement.

The problem is that although diff generation options are only relevant
for the displayed diff, a script author can imagine them affecting
path limiting.  For example, I might run

	git log -w --format=%H -- README

hoping to list commits that edited README, excluding whitespace-only
changes.  In fact, a whitespace-only change is not TREESAME so the use
of -w here has no effect (since we don't apply these diff generation
flags to the diff_options struct rev_info::pruning used for this
purpose), but the documentation suggests that it should work

	Suppose you specified foo as the <paths>. We shall call
	commits that modify foo !TREESAME, and the rest TREESAME. (In
	a diff filtered for foo, they look different and equal,
	respectively.)

and a script author who has not tested whitespace-only changes
wouldn't notice.

Similarly, a script author could include

	git log -m --first-parent --format=%H -- README

to filter the first-parent history for commits that modified README.
The -m is a no-op but it reflects the script author's intent.  For
example, until 1e20a407fe (stash list: stop passing "-m" to "git
log", 2021-05-21), "git stash list" did this.

As a result, we can't safely change "-m" to imply "-p" without fear of
breaking such scripts.  Restore the previous behavior.

Noticed because Rust's src/bootstrap/bootstrap.py made use of this
same construct: https://github.com/rust-lang/rust/pull/87513.  That
script has been updated to omit the unnecessary "-m" option, but we
can expect other scripts in the wild to have similar expectations.

Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2021-08-09 13:52:01 -07:00

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#include "diff-merges.h"
#include "revision.h"
typedef void (*diff_merges_setup_func_t)(struct rev_info *);
static void set_separate(struct rev_info *revs);
static diff_merges_setup_func_t set_to_default = set_separate;
static int suppress_parsing;
static void suppress(struct rev_info *revs)
{
revs->separate_merges = 0;
revs->first_parent_merges = 0;
revs->combine_merges = 0;
revs->dense_combined_merges = 0;
revs->combined_all_paths = 0;
revs->merges_imply_patch = 0;
revs->merges_need_diff = 0;
}
static void set_separate(struct rev_info *revs)
{
suppress(revs);
revs->separate_merges = 1;
}
static void set_first_parent(struct rev_info *revs)
{
set_separate(revs);
revs->first_parent_merges = 1;
}
static void set_combined(struct rev_info *revs)
{
suppress(revs);
revs->combine_merges = 1;
revs->dense_combined_merges = 0;
}
static void set_dense_combined(struct rev_info *revs)
{
suppress(revs);
revs->combine_merges = 1;
revs->dense_combined_merges = 1;
}
static diff_merges_setup_func_t func_by_opt(const char *optarg)
{
if (!strcmp(optarg, "off") || !strcmp(optarg, "none"))
return suppress;
if (!strcmp(optarg, "1") || !strcmp(optarg, "first-parent"))
return set_first_parent;
else if (!strcmp(optarg, "separate"))
return set_separate;
else if (!strcmp(optarg, "c") || !strcmp(optarg, "combined"))
return set_combined;
else if (!strcmp(optarg, "cc") || !strcmp(optarg, "dense-combined"))
return set_dense_combined;
else if (!strcmp(optarg, "m") || !strcmp(optarg, "on"))
return set_to_default;
return NULL;
}
static void set_diff_merges(struct rev_info *revs, const char *optarg)
{
diff_merges_setup_func_t func = func_by_opt(optarg);
if (!func)
die(_("unknown value for --diff-merges: %s"), optarg);
func(revs);
/* NOTE: the merges_need_diff flag is cleared by func() call */
if (func != suppress)
revs->merges_need_diff = 1;
}
/*
* Public functions. They are in the order they are called.
*/
int diff_merges_config(const char *value)
{
diff_merges_setup_func_t func = func_by_opt(value);
if (!func)
return -1;
set_to_default = func;
return 0;
}
void diff_merges_suppress_options_parsing(void)
{
suppress_parsing = 1;
}
int diff_merges_parse_opts(struct rev_info *revs, const char **argv)
{
int argcount = 1;
const char *optarg;
const char *arg = argv[0];
if (suppress_parsing)
return 0;
if (!strcmp(arg, "-m")) {
set_to_default(revs);
} else if (!strcmp(arg, "-c")) {
set_combined(revs);
revs->merges_imply_patch = 1;
} else if (!strcmp(arg, "--cc")) {
set_dense_combined(revs);
revs->merges_imply_patch = 1;
} else if (!strcmp(arg, "--no-diff-merges")) {
suppress(revs);
} else if (!strcmp(arg, "--combined-all-paths")) {
revs->combined_all_paths = 1;
} else if ((argcount = parse_long_opt("diff-merges", argv, &optarg))) {
set_diff_merges(revs, optarg);
} else
return 0;
revs->explicit_diff_merges = 1;
return argcount;
}
void diff_merges_suppress(struct rev_info *revs)
{
suppress(revs);
}
void diff_merges_default_to_first_parent(struct rev_info *revs)
{
if (!revs->explicit_diff_merges)
revs->separate_merges = 1;
if (revs->separate_merges)
revs->first_parent_merges = 1;
}
void diff_merges_default_to_dense_combined(struct rev_info *revs)
{
if (!revs->explicit_diff_merges)
set_dense_combined(revs);
}
void diff_merges_set_dense_combined_if_unset(struct rev_info *revs)
{
if (!revs->combine_merges)
set_dense_combined(revs);
}
void diff_merges_setup_revs(struct rev_info *revs)
{
if (suppress_parsing)
return;
if (revs->combine_merges == 0)
revs->dense_combined_merges = 0;
if (revs->separate_merges == 0)
revs->first_parent_merges = 0;
if (revs->combined_all_paths && !revs->combine_merges)
die("--combined-all-paths makes no sense without -c or --cc");
if (revs->merges_imply_patch)
revs->diff = 1;
if (revs->merges_imply_patch || revs->merges_need_diff) {
if (!revs->diffopt.output_format)
revs->diffopt.output_format = DIFF_FORMAT_PATCH;
}
}
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