pretty: add aliases for pretty formats

previously the only ways to alias a --pretty format within git were
either to set the format as your default format (via the format.pretty
configuration variable), or by using a regular git alias. This left the
definition of more complicated formats to the realm of "builtin or
nothing", with user-defined formats usually being reserved for quick
one-offs.

Here we allow user-defined formats to enjoy more or less the same
benefits of builtins. By defining pretty.myalias, "myalias" can be
used in place of whatever would normally come after --pretty=. This
can be a format:, tformat:, raw (ie, defaulting to tformat), or the name
of another builtin or user-defined pretty format.

Signed-off-by: Will Palmer <wmpalmer@gmail.com>
Reviewed-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/config.txt

@@ -1466,6 +1466,16 @@ pager.<cmd>::
 	it takes precedence over this option.  To disable pagination for
 	all commands, set `core.pager` or `GIT_PAGER` to `cat`.
 
+pretty.<name>::
+	Alias for a --pretty= format string, as specified in
+	linkgit:git-log[1]. Any aliases defined here can be used just
+	as the built-in pretty formats could. For example,
+	running `git config pretty.changelog "format:{asterisk} %H %s"`
+	would cause the invocation `git log --pretty=changelog`
+	to be equivalent to running `git log "--pretty=format:{asterisk} %H %s"`.
+	Note that an alias with the same name as a built-in format
+	will be silently ignored.
+
 pull.octopus::
 	The default merge strategy to use when pulling multiple branches
 	at once.

Documentation/pretty-formats.txt

@@ -11,7 +11,12 @@ have limited your view of history: for example, if you are
 only interested in changes related to a certain directory or
 file.
 
-Here are some additional details for each format:
+There are several built-in formats, and you can define
+additional formats by setting a pretty.<name>
+config option to either another format name, or a
+'format:' string, as described below (see
+linkgit:git-config[1]). Here are the details of the
+built-in formats:
 
 * 'oneline'
 

pretty.c

@@ -18,7 +18,9 @@ static struct cmt_fmt_map {
 	int is_alias;
 	const char *user_format;
 } *commit_formats;
+static size_t builtin_formats_len;
 static size_t commit_formats_len;
+static size_t commit_formats_alloc;
 static struct cmt_fmt_map *find_commit_format(const char *sought);
 
 static void save_user_format(struct rev_info *rev, const char *cp, int is_tformat)
@@ -30,6 +32,51 @@ static void save_user_format(struct rev_info *rev, const char *cp, int is_tforma
 	rev->commit_format = CMIT_FMT_USERFORMAT;
 }
 
+static int git_pretty_formats_config(const char *var, const char *value, void *cb)
+{
+	struct cmt_fmt_map *commit_format = NULL;
+	const char *name;
+	const char *fmt;
+	int i;
+
+	if (prefixcmp(var, "pretty."))
+		return 0;
+
+	name = var + strlen("pretty.");
+	for (i = 0; i < builtin_formats_len; i++) {
+		if (!strcmp(commit_formats[i].name, name))
+			return 0;
+	}
+
+	for (i = builtin_formats_len; i < commit_formats_len; i++) {
+		if (!strcmp(commit_formats[i].name, name)) {
+			commit_format = &commit_formats[i];
+			break;
+		}
+	}
+
+	if (!commit_format) {
+		ALLOC_GROW(commit_formats, commit_formats_len+1,
+			   commit_formats_alloc);
+		commit_format = &commit_formats[commit_formats_len];
+		commit_formats_len++;
+	}
+
+	commit_format->name = xstrdup(name);
+	commit_format->format = CMIT_FMT_USERFORMAT;
+	git_config_string(&fmt, var, value);
+	if (!prefixcmp(fmt, "format:") || !prefixcmp(fmt, "tformat:")) {
+		commit_format->is_tformat = fmt[0] == 't';
+		fmt = strchr(fmt, ':') + 1;
+	} else if (strchr(fmt, '%'))
+		commit_format->is_tformat = 1;
+	else
+		commit_format->is_alias = 1;
+	commit_format->user_format = fmt;
+
+	return 0;
+}
+
 static void setup_commit_formats(void)
 {
 	struct cmt_fmt_map builtin_formats[] = {
@@ -42,10 +89,12 @@ static void setup_commit_formats(void)
 		{ "oneline",	CMIT_FMT_ONELINE,	1 }
 	};
 	commit_formats_len = ARRAY_SIZE(builtin_formats);
-	commit_formats = xmalloc(commit_formats_len *
-				 sizeof(*builtin_formats));
+	builtin_formats_len = commit_formats_len;
+	ALLOC_GROW(commit_formats, commit_formats_len, commit_formats_alloc);
 	memcpy(commit_formats, builtin_formats,
 	       sizeof(*builtin_formats)*ARRAY_SIZE(builtin_formats));
+
+	git_config(git_pretty_formats_config, NULL);
 }
 
 static struct cmt_fmt_map *find_commit_format_recursive(const char *sought,
@@ -116,6 +165,10 @@ void get_commit_format(const char *arg, struct rev_info *rev)
 
 	rev->commit_format = commit_format->format;
 	rev->use_terminator = commit_format->is_tformat;
+	if (commit_format->format == CMIT_FMT_USERFORMAT) {
+		save_user_format(rev, commit_format->user_format,
+				 commit_format->is_tformat);
+	}
 }
 
 /*

t/t4205-log-pretty-formats.sh

@@ -0,0 +1,74 @@
+#!/bin/sh
+#
+# Copyright (c) 2010, Will Palmer
+#
+
+test_description='Test pretty formats'
+. ./test-lib.sh
+
+test_expect_success 'set up basic repos' '
+	>foo &&
+	>bar &&
+	git add foo &&
+	test_tick &&
+	git commit -m initial &&
+	git add bar &&
+	test_tick &&
+	git commit -m "add bar"
+'
+
+test_expect_success 'alias builtin format' '
+	git log --pretty=oneline >expected &&
+	git config pretty.test-alias oneline &&
+	git log --pretty=test-alias >actual &&
+	test_cmp expected actual
+'
+
+test_expect_success 'alias masking builtin format' '
+	git log --pretty=oneline >expected &&
+	git config pretty.oneline "%H" &&
+	git log --pretty=oneline >actual &&
+	test_cmp expected actual
+'
+
+test_expect_success 'alias user-defined format' '
+	git log --pretty="format:%h" >expected &&
+	git config pretty.test-alias "format:%h" &&
+	git log --pretty=test-alias >actual &&
+	test_cmp expected actual
+'
+
+test_expect_success 'alias user-defined tformat' '
+	git log --pretty="tformat:%h" >expected &&
+	git config pretty.test-alias "tformat:%h" &&
+	git log --pretty=test-alias >actual &&
+	test_cmp expected actual
+'
+
+test_expect_success 'alias non-existant format' '
+	git config pretty.test-alias format-that-will-never-exist &&
+	test_must_fail git log --pretty=test-alias
+'
+
+test_expect_success 'alias of an alias' '
+	git log --pretty="tformat:%h" >expected &&
+	git config pretty.test-foo "tformat:%h" &&
+	git config pretty.test-bar test-foo &&
+	git log --pretty=test-bar >actual && test_cmp expected actual
+'
+
+test_expect_success 'alias masking an alias' '
+	git log --pretty=format:"Two %H" >expected &&
+	git config pretty.duplicate "format:One %H" &&
+	git config --add pretty.duplicate "format:Two %H" &&
+	git log --pretty=duplicate >actual &&
+	test_cmp expected actual
+'
+
+test_expect_success 'alias loop' '
+	git config pretty.test-foo test-bar &&
+	git config pretty.test-bar test-foo &&
+	test_must_fail git log --pretty=test-foo
+'
+
+test_done