[PATCH 5/8] builtin/config: canonicalize "value_regex" with `--type=bool`

["Martin Ågren" <martin.agren@gmail.com>]

With `--type=bool`, we use the "value_regex" as a normal regex and do
not use our knowledge about the different well-defined ways we have of
spelling the boolean values. Let's consider a few examples.

These output "true":
	git -c foo.bar=true config --type=bool --get foo.bar true
	git -c foo.bar=true config --type=bool --get foo.bar t

These produce no output:
	git -c foo.bar=true config --type=bool --get foo.bar True
	git -c foo.bar=true config --type=bool --get foo.bar 1

Canonicalize the provided "value_regex", then canonicalize candidate
values as we go through the config and compare the canonicalized values.
If the parameter doesn't canonicalize, fall back to handling it as a
regex, as before. This would happen in the second example above, but
also if someone has hand-rolled their own canonicalisation with, e.g.,
something like "^(on|On|ON|true|1|42)$".

This commit affects all modes that take a "value_regex", e.g.,
`--get-regexp` which can be used in a more useful way than the examples
above might at first suggest:

	git config --type=bool --name-only --get-regexp '^foo\.' true

This commit does change the behavior for certain usages, but it almost
certainly does so for the better: We don't exclude config items based on
how the config happens to spell "true" or "false". This commit would
cause a regression if someone uses different synonyms for "true",
knowing that Git handles them all the same in day-to-day operation, but
relying on the encoding (using, say, integers 1-100) to signal some sort
of confidence and using `git config` to query for various such "levels".
I'm tempted to bet no-one will be hurt by this change.

Do not rename the "value_regex" in the documentation. This commit can be
seen as teaching `git config --type=bool` about a particular type of
regex, where "true" matches "yes", but not "no". So arguably,
"value_regex" still describes quite well what is going on.

Signed-off-by: Martin Ågren <martin.agren@gmail.com>
---
 Documentation/git-config.txt |  4 ++++
 builtin/config.c             | 15 +++++++++++-
 t/t1300-config.sh            | 45 ++++++++++++++++++++++++++++++++++++
 3 files changed, 63 insertions(+), 1 deletion(-)

diff --git a/Documentation/git-config.txt b/Documentation/git-config.txt
index 899e92a1c9..139750bbda 100644
--- a/Documentation/git-config.txt
+++ b/Documentation/git-config.txt
@@ -43,6 +43,10 @@ outgoing values are canonicalize-able under the given <type>.  If no
 `--type=<type>` is given, no canonicalization will be performed. Callers may
 unset an existing `--type` specifier with `--no-type`.
 
+With `--type=bool`, if `value_regex` is given
+and canonicalizes to a boolean value, it matches all entries
+that canonicalize to the same boolean value.
+
 When reading, the values are read from the system, global and
 repository local configuration files by default, and options
 `--system`, `--global`, `--local`, `--worktree` and
diff --git a/builtin/config.c b/builtin/config.c
index d812e73e2b..c9fe0c5752 100644
--- a/builtin/config.c
+++ b/builtin/config.c
@@ -15,9 +15,10 @@ static const char *const builtin_config_usage[] = {
 static char *key;
 static regex_t *key_regexp;
 static struct {
-	enum { none, regexp } mode;
+	enum { none, regexp, boolean } mode;
 	regex_t *regexp;
 	int do_not_match; /* used with `regexp` */
+	int boolean;
 } cmd_line_value;
 static int show_keys;
 static int omit_values;
@@ -278,6 +279,9 @@ static int collect_config(const char *key_, const char *value_, void *cb)
 	     !!regexec(cmd_line_value.regexp, value_ ? value_ : "",
 		       0, NULL, 0)))
 		return 0;
+	if (cmd_line_value.mode == boolean &&
+	    git_parse_maybe_bool(value_) != cmd_line_value.boolean)
+		return 0;
 
 	ALLOC_GROW(values->items, values->nr + 1, values->alloc);
 	strbuf_init(&values->items[values->nr], 0);
@@ -292,6 +296,15 @@ static int handle_value_regex(const char *regex_)
 		return 0;
 	}
 
+	if (type == TYPE_BOOL) {
+		int boolval = git_parse_maybe_bool(regex_);
+		if (boolval >= 0) {
+			cmd_line_value.mode = boolean;
+			cmd_line_value.boolean = boolval;
+			return 0;
+		}
+	}
+
 	cmd_line_value.mode = regexp;
 
 	if (regex_[0] == '!') {
diff --git a/t/t1300-config.sh b/t/t1300-config.sh
index a38cc143a1..e4906a893e 100755
--- a/t/t1300-config.sh
+++ b/t/t1300-config.sh
@@ -427,6 +427,51 @@ test_expect_success 'no arguments, but no crash' '
 	test_i18ngrep usage output
 '
 
+test_expect_success 'setup config file with several boolean values' '
+	cat >.git/config <<-\EOF
+	[foo]
+		n1 = no
+		n2 = NO
+		n3 = off
+		n4 = false
+		n5 = 0
+		n6 =
+		y1 = yes
+		y2 = YES
+		y3 = on
+		y4 = true
+		y5 = 1
+		y6 = 42
+		y7
+	EOF
+'
+
+test_expect_success '--get-regexp canonicalizes value_regex with --type=bool (false)' '
+	git config --type=bool --get-regexp "foo\..*" OFF >output &&
+	test_line_count = 6 output &&
+	! grep -v "^foo.n" output
+'
+
+test_expect_success '--get-regexp canonicalizes value_regex with --type=bool (true)' '
+	git config --type=bool --get-regexp "foo\..*" ON >output &&
+	test_line_count = 7 output &&
+	! grep -v "^foo.y" output
+'
+
+test_expect_success '--get canonicalizes integer value_regex with --type=bool' '
+	echo true >expect &&
+	git config --type=bool --get foo.y2 1 >output &&
+	test_cmp expect output
+'
+
+test_expect_success '--type=bool with "non-bool" value_regex' '
+	echo true >expect &&
+	git config --type=bool --get foo.y4 "t.*" >output &&
+	test_cmp expect output &&
+	test_must_fail git config --type=bool --get foo.y4 "T.*" >output &&
+	test_must_be_empty output
+'
+
 test_expect_success 'setup simple config file' '
 	q_to_tab >.git/config <<-\EOF
 	[a.b]
-- 
2.24.0