[PATCH v2 3/4] log: add a log.graph config option

[Alex Henrie <alexhenrie24@gmail.com>]

A coworker recently asked me how to turn on --graph by default in
`git log`. I googled it and found that several people have asked that
before on Stack Overflow, with no good solution:
https://stackoverflow.com/questions/43555256/how-do-i-make-git-log-graph-the-default

Add a log.graph option to turn on graph mode in the absence of any
incompatible options.

Signed-off-by: Alex Henrie <alexhenrie24@gmail.com>
---
v2: ensure that --no-graph on the command line takes precedence over
log.graph=true in the config file
---
 Documentation/config/log.txt |  5 +++++
 Documentation/git-log.txt    |  5 +++++
 builtin/log.c                |  6 ++++++
 revision.c                   | 10 +++++++++
 revision.h                   |  2 ++
 t/t4202-log.sh               | 42 ++++++++++++++++++++++++++++++++++++
 6 files changed, 70 insertions(+)

diff --git a/Documentation/config/log.txt b/Documentation/config/log.txt
index 456eb07800..3e356cfce6 100644
--- a/Documentation/config/log.txt
+++ b/Documentation/config/log.txt
@@ -35,6 +35,11 @@ log.follow::
 	i.e. it cannot be used to follow multiple files and does not work well
 	on non-linear history.
 
+log.graph::
+	If true, makes linkgit:git-log[1], linkgit:git-show[1], and
+	linkgit:git-whatchanged[1] assume `--graph` unless an incompatible
+	option is also specified.
+
 log.graphColors::
 	A list of colors, separated by commas, that can be used to draw
 	history lines in `git log --graph`.
diff --git a/Documentation/git-log.txt b/Documentation/git-log.txt
index 20e87cecf4..7e9e0f8afe 100644
--- a/Documentation/git-log.txt
+++ b/Documentation/git-log.txt
@@ -214,6 +214,11 @@ log.follow::
 	i.e. it cannot be used to follow multiple files and does not work well
 	on non-linear history.
 
+log.graph::
+	If `true`, `git log` and related commands will act as if the
+	`--graph` option was passed to them unless an incompatible option is
+	also specified.
+
 log.showRoot::
 	If `false`, `git log` and related commands will not treat the
 	initial commit as a big creation event.  Any root commits in
diff --git a/builtin/log.c b/builtin/log.c
index 4b493408cc..5eaefab046 100644
--- a/builtin/log.c
+++ b/builtin/log.c
@@ -48,6 +48,7 @@ static int default_show_root = 1;
 static int default_follow;
 static int default_show_signature;
 static int default_encode_email_headers = 1;
+static int default_graph;
 static int decoration_style;
 static int decoration_given;
 static int use_mailmap_config = 1;
@@ -156,6 +157,7 @@ static void cmd_log_init_defaults(struct rev_info *rev)
 	rev->show_signature = default_show_signature;
 	rev->encode_email_headers = default_encode_email_headers;
 	rev->diffopt.flags.allow_textconv = 1;
+	rev->graph_default = default_graph;
 
 	if (default_date_mode)
 		parse_date_format(default_date_mode, &rev->date_mode);
@@ -519,6 +521,10 @@ static int git_log_config(const char *var, const char *value, void *cb)
 		default_show_signature = git_config_bool(var, value);
 		return 0;
 	}
+	if (!strcmp(var, "log.graph")) {
+		default_graph = git_config_bool(var, value);
+		return 0;
+	}
 
 	if (grep_config(var, value, cb) < 0)
 		return -1;
diff --git a/revision.c b/revision.c
index a39fd1c278..55e12cd401 100644
--- a/revision.c
+++ b/revision.c
@@ -2426,9 +2426,11 @@ static int handle_revision_opt(struct rev_info *revs, int argc, const char **arg
 	} else if (!strcmp(arg, "--graph")) {
 		graph_clear(revs->graph);
 		revs->graph = graph_init(revs);
+		revs->graph_default = 0;
 	} else if (!strcmp(arg, "--no-graph")) {
 		graph_clear(revs->graph);
 		revs->graph = NULL;
+		revs->graph_default = 0;
 	} else if (!strcmp(arg, "--encode-email-headers")) {
 		revs->encode_email_headers = 1;
 	} else if (!strcmp(arg, "--no-encode-email-headers")) {
@@ -2796,6 +2798,14 @@ int setup_revisions(int argc, const char **argv, struct rev_info *revs, struct s
 			break;
 		}
 	}
+	if (revs->graph_default &&
+	    !revs->graph &&
+	    /* check for incompatible options */
+	    !revs->track_linear &&
+	    !revs->reverse &&
+	    !revs->reflog_info &&
+	    !revs->no_walk)
+		revs->graph = graph_init(revs);
 	revision_opts_finish(revs);
 
 	if (prune_data.nr) {
diff --git a/revision.h b/revision.h
index 5a507db202..62a0ef4c53 100644
--- a/revision.h
+++ b/revision.h
@@ -249,6 +249,8 @@ struct rev_info {
 
 	/* Display history graph */
 	struct git_graph *graph;
+	/* whether to initialize graph if it has not been initialized already */
+	int graph_default;
 
 	/* special limits */
 	int skip_count;
diff --git a/t/t4202-log.sh b/t/t4202-log.sh
index f3f36a7e01..e9695510c3 100755
--- a/t/t4202-log.sh
+++ b/t/t4202-log.sh
@@ -1695,6 +1695,20 @@ test_expect_success '--no-graph does not unset --parents' '
 	test_cmp expect actual
 '
 
+test_expect_success 'log.graph=true behaves like --graph' '
+	git log --graph >expect &&
+	test_config log.graph true &&
+	git log >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success '--no-graph countermands log.graph=true' '
+	git log >expect &&
+	test_config log.graph true &&
+	git log --no-graph >actual &&
+	test_cmp expect actual
+'
+
 test_expect_success '--reverse and --graph conflict' '
 	test_must_fail git log --reverse --graph 2>stderr &&
 	test_i18ngrep "cannot be used together" stderr
@@ -1706,6 +1720,13 @@ test_expect_success '--reverse --graph --no-graph works' '
 	test_cmp expect actual
 '
 
+test_expect_success '--reverse ignores log.graph' '
+	git log --reverse >expect &&
+	test_config log.graph true &&
+	git log --reverse >actual &&
+	test_cmp expect actual
+'
+
 test_expect_success '--show-linear-break and --graph conflict' '
 	test_must_fail git log --show-linear-break --graph 2>stderr &&
 	test_i18ngrep "cannot be used together" stderr
@@ -1717,6 +1738,13 @@ test_expect_success '--show-linear-break --graph --no-graph works' '
 	test_cmp expect actual
 '
 
+test_expect_success '--show-linear-break ignores log.graph' '
+	git log --show-linear-break >expect &&
+	test_config log.graph true &&
+	git log --show-linear-break >actual &&
+	test_cmp expect actual
+'
+
 test_expect_success '--no-walk and --graph conflict' '
 	test_must_fail git log --no-walk --graph 2>stderr &&
 	test_i18ngrep "cannot be used together" stderr
@@ -1728,6 +1756,13 @@ test_expect_success '--no-walk --graph --no-graph works' '
 	test_cmp expect actual
 '
 
+test_expect_success '--no-walk ignores log.graph' '
+	git log --no-walk >expect &&
+	test_config log.graph true &&
+	git log --no-walk >actual &&
+	test_cmp expect actual
+'
+
 test_expect_success '--walk-reflogs and --graph conflict' '
 	test_must_fail git log --walk-reflogs --graph 2>stderr &&
 	test_i18ngrep -E "(cannot combine|cannot be used together)" stderr
@@ -1739,6 +1774,13 @@ test_expect_success '--walk-reflogs --graph --no-graph works' '
 	test_cmp expect actual
 '
 
+test_expect_success '--walk-reflogs ignores log.graph' '
+	git log --walk-reflogs >expect &&
+	test_config log.graph true &&
+	git log --walk-reflogs >actual &&
+	test_cmp expect actual
+'
+
 test_expect_success 'dotdot is a parent directory' '
 	mkdir -p a/b &&
 	( echo sixth && echo fifth ) >expect &&
-- 
2.32.0.2645.gc109162a1f