Merge branch 'jk/format-patch-ignore-noprefix'

"git format-patch" honors the src/dst prefixes set to nonstandard
values with configuration variables like "diff.noprefix", causing
receiving end of the patch that expects the standard -p1 format to
break.  Teach "format-patch" to ignore end-user configuration and
always use the standard prefixes.

This is a backward compatibility breaking change.

* jk/format-patch-ignore-noprefix:
  rebase: prefer --default-prefix to --{src,dst}-prefix for format-patch
  format-patch: add format.noprefix option
  format-patch: do not respect diff.noprefix
  diff: add --default-prefix option
  t4013: add tests for diff prefix options
  diff: factor out src/dst prefix setup

8 files changed, 118 insertions, 6 deletions

diff --git a/Documentation/config/format.txt b/Documentation/config/format.txt
index 73678d88a1..8cf6f00d93 100644
--- a/Documentation/config/format.txt
+++ b/Documentation/config/format.txt
@@ -144,3 +144,10 @@ will only show notes from `refs/notes/bar`.
 format.mboxrd::
 	A boolean value which enables the robust "mboxrd" format when
 	`--stdout` is in use to escape "^>+From " lines.
+
+format.noprefix::
+	If set, do not show any source or destination prefix in patches.
+	This is equivalent to the `diff.noprefix` option used by `git
+	diff` (but which is not respected by `format-patch`). Note that
+	by setting this, the receiver of any patches you generate will
+	have to apply them using the `-p0` option.
diff --git a/Documentation/diff-options.txt b/Documentation/diff-options.txt
index 7d73e976d9..08ab86189a 100644
--- a/Documentation/diff-options.txt
+++ b/Documentation/diff-options.txt
@@ -852,6 +852,11 @@ endif::git-format-patch[]
 --no-prefix::
 	Do not show any source or destination prefix.
 
+--default-prefix::
+	Use the default source and destination prefixes ("a/" and "b/").
+	This is usually the default already, but may be used to override
+	config such as `diff.noprefix`.
+
 --line-prefix=<prefix>::
 	Prepend an additional prefix to every line of output.
 
diff --git a/builtin/log.c b/builtin/log.c
index bc204ea76f..4693385e8e 100644
--- a/builtin/log.c
+++ b/builtin/log.c
@@ -58,6 +58,7 @@ static int stdout_mboxrd;
 static const char *fmt_patch_subject_prefix = "PATCH";
 static int fmt_patch_name_max = FORMAT_PATCH_NAME_MAX_DEFAULT;
 static const char *fmt_pretty;
+static int format_no_prefix;
 
 static const char * const builtin_log_usage[] = {
 	N_("git log [<options>] [<revision-range>] [[--] <path>...]"),
@@ -1084,6 +1085,19 @@ static int git_format_config(const char *var, const char *value, void *cb)
 		stdout_mboxrd = git_config_bool(var, value);
 		return 0;
 	}
+	if (!strcmp(var, "format.noprefix")) {
+		format_no_prefix = 1;
+		return 0;
+	}
+
+	/*
+	 * ignore some porcelain config which would otherwise be parsed by
+	 * git_diff_ui_config(), via git_log_config(); we can't just avoid
+	 * diff_ui_config completely, because we do care about some ui options
+	 * like color.
+	 */
+	if (!strcmp(var, "diff.noprefix"))
+		return 0;
 
 	return git_log_config(var, value, cb);
 }
@@ -1993,6 +2007,9 @@ int cmd_format_patch(int argc, const char **argv, const char *prefix)
 	s_r_opt.def = "HEAD";
 	s_r_opt.revarg_opt = REVARG_COMMITTISH;
 
+	if (format_no_prefix)
+		diff_set_noprefix(&rev.diffopt);
+
 	if (default_attach) {
 		rev.mime_boundary = default_attach;
 		rev.no_inline = 1;
diff --git a/builtin/rebase.c b/builtin/rebase.c
index dd31d5ab91..5b7b908b66 100644
--- a/builtin/rebase.c
+++ b/builtin/rebase.c
@@ -661,7 +661,7 @@ static int run_am(struct rebase_options *opts)
 	format_patch.git_cmd = 1;
 	strvec_pushl(&format_patch.args, "format-patch", "-k", "--stdout",
 		     "--full-index", "--cherry-pick", "--right-only",
-		     "--src-prefix=a/", "--dst-prefix=b/", "--no-renames",
+		     "--default-prefix", "--no-renames",
 		     "--no-cover-letter", "--pretty=mboxrd", "--topo-order",
 		     "--no-base", NULL);
 	if (opts->git_format_patch_opt.len)
diff --git a/diff.c b/diff.c
index 00d47281a1..1617aa50a9 100644
--- a/diff.c
+++ b/diff.c
@@ -3376,6 +3376,17 @@ void diff_set_mnemonic_prefix(struct diff_options *options, const char *a, const
 		options->b_prefix = b;
 }
 
+void diff_set_noprefix(struct diff_options *options)
+{
+	options->a_prefix = options->b_prefix = "";
+}
+
+void diff_set_default_prefix(struct diff_options *options)
+{
+	options->a_prefix = "a/";
+	options->b_prefix = "b/";
+}
+
 struct userdiff_driver *get_textconv(struct repository *r,
 				     struct diff_filespec *one)
 {
@@ -4676,10 +4687,9 @@ void repo_diff_setup(struct repository *r, struct diff_options *options)
 		options->flags.ignore_untracked_in_submodules = 1;
 
 	if (diff_no_prefix) {
-		options->a_prefix = options->b_prefix = "";
+		diff_set_noprefix(options);
 	} else if (!diff_mnemonic_prefix) {
-		options->a_prefix = "a/";
-		options->b_prefix = "b/";
+		diff_set_default_prefix(options);
 	}
 
 	options->color_moved = diff_color_moved_default;
@@ -5263,8 +5273,18 @@ static int diff_opt_no_prefix(const struct option *opt,
 
 	BUG_ON_OPT_NEG(unset);
 	BUG_ON_OPT_ARG(optarg);
-	options->a_prefix = "";
-	options->b_prefix = "";
+	diff_set_noprefix(options);
+	return 0;
+}
+
+static int diff_opt_default_prefix(const struct option *opt,
+				   const char *optarg, int unset)
+{
+	struct diff_options *options = opt->value;
+
+	BUG_ON_OPT_NEG(unset);
+	BUG_ON_OPT_ARG(optarg);
+	diff_set_default_prefix(options);
 	return 0;
 }
 
@@ -5557,6 +5577,9 @@ struct option *add_diff_options(const struct option *opts,
 		OPT_CALLBACK_F(0, "no-prefix", options, NULL,
 			       N_("do not show any source or destination prefix"),
 			       PARSE_OPT_NONEG | PARSE_OPT_NOARG, diff_opt_no_prefix),
+		OPT_CALLBACK_F(0, "default-prefix", options, NULL,
+			       N_("use default prefixes a/ and b/"),
+			       PARSE_OPT_NONEG | PARSE_OPT_NOARG, diff_opt_default_prefix),
 		OPT_INTEGER_F(0, "inter-hunk-context", &options->interhunkcontext,
 			      N_("show context between diff hunks up to the specified number of lines"),
 			      PARSE_OPT_NONEG),
diff --git a/diff.h b/diff.h
index 3520119b00..09627f6e84 100644
--- a/diff.h
+++ b/diff.h
@@ -496,6 +496,8 @@ void diff_tree_combined(const struct object_id *oid, const struct oid_array *par
 void diff_tree_combined_merge(const struct commit *commit, struct rev_info *rev);
 
 void diff_set_mnemonic_prefix(struct diff_options *options, const char *a, const char *b);
+void diff_set_noprefix(struct diff_options *options);
+void diff_set_default_prefix(struct diff_options *options);
 
 int diff_can_quit_early(struct diff_options *);
 
diff --git a/t/t4013-diff-various.sh b/t/t4013-diff-various.sh
index dfcf3a0aaa..5de1d19075 100755
--- a/t/t4013-diff-various.sh
+++ b/t/t4013-diff-various.sh
@@ -616,4 +616,46 @@ test_expect_success 'diff -I<regex>: detect malformed regex' '
 	test_i18ngrep "invalid regex given to -I: " error
 '
 
+# check_prefix <patch> <src> <dst>
+# check only lines with paths to avoid dependency on exact oid/contents
+check_prefix () {
+	grep -E '^(diff|---|\+\+\+) ' "$1" >actual.paths &&
+	cat >expect <<-EOF &&
+	diff --git $2 $3
+	--- $2
+	+++ $3
+	EOF
+	test_cmp expect actual.paths
+}
+
+test_expect_success 'diff-files does not respect diff.noprefix' '
+	git -c diff.noprefix diff-files -p >actual &&
+	check_prefix actual a/file0 b/file0
+'
+
+test_expect_success 'diff-files respects --no-prefix' '
+	git diff-files -p --no-prefix >actual &&
+	check_prefix actual file0 file0
+'
+
+test_expect_success 'diff respects diff.noprefix' '
+	git -c diff.noprefix diff >actual &&
+	check_prefix actual file0 file0
+'
+
+test_expect_success 'diff --default-prefix overrides diff.noprefix' '
+	git -c diff.noprefix diff --default-prefix >actual &&
+	check_prefix actual a/file0 b/file0
+'
+
+test_expect_success 'diff respects diff.mnemonicprefix' '
+	git -c diff.mnemonicprefix diff >actual &&
+	check_prefix actual i/file0 w/file0
+'
+
+test_expect_success 'diff --default-prefix overrides diff.mnemonicprefix' '
+	git -c diff.mnemonicprefix diff --default-prefix >actual &&
+	check_prefix actual a/file0 b/file0
+'
+
 test_done
diff --git a/t/t4014-format-patch.sh b/t/t4014-format-patch.sh
index ffc7c60680..8c3d06622a 100755
--- a/t/t4014-format-patch.sh
+++ b/t/t4014-format-patch.sh
@@ -2396,4 +2396,20 @@ test_expect_success 'interdiff: solo-patch' '
 	test_cmp expect actual
 '
 
+test_expect_success 'format-patch does not respect diff.noprefix' '
+	git -c diff.noprefix format-patch -1 --stdout >actual &&
+	grep "^--- a/blorp" actual
+'
+
+test_expect_success 'format-patch respects format.noprefix' '
+	git -c format.noprefix format-patch -1 --stdout >actual &&
+	grep "^--- blorp" actual
+'
+
+test_expect_success 'format-patch --default-prefix overrides format.noprefix' '
+	git -c format.noprefix \
+		format-patch -1 --default-prefix --stdout >actual &&
+	grep "^--- a/blorp" actual
+'
+
 test_done