pretty: find pretty formats case-insensitively

User-defined pretty formats are stored in config, which is meant to use
case-insensitive matching for names as noted in config.txt's 'Syntax'
section:

    All the other lines [...] are recognized as setting variables, in
    the form 'name = value' [...]. The variable names are
    case-insensitive, [...].

When a user specifies one of their format aliases with an uppercase in
it, however, it is not found.

    $ git config pretty.testAlias %h
    $ git config --list | grep pretty
    pretty.testalias=%h
    $ git log --format=testAlias -1
    fatal: invalid --pretty format: testAlias
    $ git log --format=testalias -1
    3c2a3fd

This is true whether the name in the config file uses any uppercase
characters or not.

Use case-insensitive comparisons when identifying format aliases.

Co-authored-by: Jeff King <peff@peff.net>
Signed-off-by: Brian Lyles <brianmlyles@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: 2 people

pretty.c

@@ -140,7 +140,7 @@ static struct cmt_fmt_map *find_commit_format_recursive(const char *sought,
 	for (i = 0; i < commit_formats_len; i++) {
 		size_t match_len;
 
-		if (!starts_with(commit_formats[i].name, sought))
+		if (!istarts_with(commit_formats[i].name, sought))
 			continue;
 
 		match_len = strlen(commit_formats[i].name);

t/t4205-log-pretty-formats.sh

@@ -58,6 +58,14 @@ test_expect_success 'alias user-defined format' '
 	test_cmp expected actual
 '
 
+test_expect_success 'alias user-defined format is matched case-insensitively' '
+	git log --pretty="format:%h" >expected &&
+	test_config pretty.testone "format:%h" &&
+	test_config pretty.testtwo testOne &&
+	git log --pretty=testTwo >actual &&
+	test_cmp expected actual
+'
+
 test_expect_success 'alias user-defined tformat with %s (ISO8859-1 encoding)' '
 	test_config i18n.logOutputEncoding $test_encoding &&
 	git log --oneline >expected-s &&