Merge branch 'jk/color-and-pager'

* jk/color-and-pager:
  want_color: automatically fallback to color.ui
  diff: don't load color config in plumbing
  config: refactor get_colorbool function
  color: delay auto-color decision until point of use
  git_config_colorbool: refactor stdout_is_tty handling
  diff: refactor COLOR_DIFF from a flag into an int
  setup_pager: set GIT_PAGER_IN_USE
  t7006: use test_config helpers
  test-lib: add helper functions for config
  t7006: modernize calls to unset

Conflicts:
	builtin/commit.c
	parse-options.c

21 files changed, 176 insertions, 147 deletions

diff --git a/builtin/branch.c b/builtin/branch.c
index 953bc1c..f7da69c 100644
--- a/builtin/branch.c
+++ b/builtin/branch.c
@@ -71,7 +71,7 @@ static int parse_branch_color_slot(const char *var, int ofs)
 static int git_branch_config(const char *var, const char *value, void *cb)
 {
 	if (!strcmp(var, "color.branch")) {
-		branch_use_color = git_config_colorbool(var, value, -1);
+		branch_use_color = git_config_colorbool(var, value);
 		return 0;
 	}
 	if (!prefixcmp(var, "color.branch.")) {
@@ -88,7 +88,7 @@ static int git_branch_config(const char *var, const char *value, void *cb)
 
 static const char *branch_get_color(enum color_branch ix)
 {
-	if (branch_use_color > 0)
+	if (want_color(branch_use_color))
 		return branch_colors[ix];
 	return "";
 }
@@ -673,9 +673,6 @@ int cmd_branch(int argc, const char **argv, const char *prefix)
 
 	git_config(git_branch_config, NULL);
 
-	if (branch_use_color == -1)
-		branch_use_color = git_use_color_default;
-
 	track = git_branch_track;
 
 	head = resolve_ref("HEAD", head_sha1, 0, NULL);
diff --git a/builtin/commit.c b/builtin/commit.c
index 05029d40..cbc9613 100644
--- a/builtin/commit.c
+++ b/builtin/commit.c
@@ -1141,7 +1141,7 @@ static int git_status_config(const char *k, const char *v, void *cb)
 		return 0;
 	}
 	if (!strcmp(k, "status.color") || !strcmp(k, "color.status")) {
-		s->use_color = git_config_colorbool(k, v, -1);
+		s->use_color = git_config_colorbool(k, v);
 		return 0;
 	}
 	if (!prefixcmp(k, "status.color.") || !prefixcmp(k, "color.status.")) {
@@ -1234,10 +1234,6 @@ int cmd_status(int argc, const char **argv, const char *prefix)
 
 	if (s.relative_paths)
 		s.prefix = prefix;
-	if (s.use_color == -1)
-		s.use_color = git_use_color_default;
-	if (diff_use_color_default == -1)
-		diff_use_color_default = git_use_color_default;
 
 	switch (status_format) {
 	case STATUS_FORMAT_SHORT:
@@ -1393,8 +1389,6 @@ int cmd_commit(int argc, const char **argv, const char *prefix)
 	git_config(git_commit_config, &s);
 	determine_whence(&s);
 
-	if (s.use_color == -1)
-		s.use_color = git_use_color_default;
 	if (get_sha1("HEAD", sha1))
 		current_head = NULL;
 	else {
@@ -1404,11 +1398,8 @@ int cmd_commit(int argc, const char **argv, const char *prefix)
 	}
 	argc = parse_and_validate_options(argc, argv, builtin_commit_usage,
 					  prefix, current_head, &s);
-	if (dry_run) {
-		if (diff_use_color_default == -1)
-			diff_use_color_default = git_use_color_default;
+	if (dry_run)
 		return dry_run_commit(argc, argv, prefix, current_head, &s);
-	}
 	index_file = prepare_index(argc, argv, prefix, current_head, 0);
 
 	/* Set up everything for writing the commit object.  This includes
diff --git a/builtin/config.c b/builtin/config.c
index 211e118..0b4ecac 100644
--- a/builtin/config.c
+++ b/builtin/config.c
@@ -303,24 +303,18 @@ static void get_color(const char *def_color)
 	fputs(parsed_color, stdout);
 }
 
-static int stdout_is_tty;
 static int get_colorbool_found;
 static int get_diff_color_found;
+static int get_color_ui_found;
 static int git_get_colorbool_config(const char *var, const char *value,
 		void *cb)
 {
-	if (!strcmp(var, get_colorbool_slot)) {
-		get_colorbool_found =
-			git_config_colorbool(var, value, stdout_is_tty);
-	}
-	if (!strcmp(var, "diff.color")) {
-		get_diff_color_found =
-			git_config_colorbool(var, value, stdout_is_tty);
-	}
-	if (!strcmp(var, "color.ui")) {
-		git_use_color_default = git_config_colorbool(var, value, stdout_is_tty);
-		return 0;
-	}
+	if (!strcmp(var, get_colorbool_slot))
+		get_colorbool_found = git_config_colorbool(var, value);
+	else if (!strcmp(var, "diff.color"))
+		get_diff_color_found = git_config_colorbool(var, value);
+	else if (!strcmp(var, "color.ui"))
+		get_color_ui_found = git_config_colorbool(var, value);
 	return 0;
 }
 
@@ -334,9 +328,11 @@ static int get_colorbool(int print)
 		if (!strcmp(get_colorbool_slot, "color.diff"))
 			get_colorbool_found = get_diff_color_found;
 		if (get_colorbool_found < 0)
-			get_colorbool_found = git_use_color_default;
+			get_colorbool_found = get_color_ui_found;
 	}
 
+	get_colorbool_found = want_color(get_colorbool_found);
+
 	if (print) {
 		printf("%s\n", get_colorbool_found ? "true" : "false");
 		return 0;
@@ -510,9 +506,7 @@ int cmd_config(int argc, const char **argv, const char *prefix)
 	}
 	else if (actions == ACTION_GET_COLORBOOL) {
 		if (argc == 1)
-			stdout_is_tty = git_config_bool("command line", argv[0]);
-		else if (argc == 0)
-			stdout_is_tty = isatty(1);
+			color_stdout_is_tty = git_config_bool("command line", argv[0]);
 		return get_colorbool(argc != 0);
 	}
 
diff --git a/builtin/diff.c b/builtin/diff.c
index 69cd5ee..1118689 100644
--- a/builtin/diff.c
+++ b/builtin/diff.c
@@ -277,9 +277,6 @@ int cmd_diff(int argc, const char **argv, const char *prefix)
 	gitmodules_config();
 	git_config(git_diff_ui_config, NULL);
 
-	if (diff_use_color_default == -1)
-		diff_use_color_default = git_use_color_default;
-
 	init_revisions(&rev, prefix);
 
 	/* If this is a no-index diff, just run it and exit there. */
diff --git a/builtin/grep.c b/builtin/grep.c
index 1851797..1c359c2 100644
--- a/builtin/grep.c
+++ b/builtin/grep.c
@@ -325,7 +325,7 @@ static int grep_config(const char *var, const char *value, void *cb)
 	}
 
 	if (!strcmp(var, "color.grep"))
-		opt->color = git_config_colorbool(var, value, -1);
+		opt->color = git_config_colorbool(var, value);
 	else if (!strcmp(var, "color.grep.context"))
 		color = opt->color_context;
 	else if (!strcmp(var, "color.grep.filename"))
@@ -898,8 +898,6 @@ int cmd_grep(int argc, const char **argv, const char *prefix)
 	strcpy(opt.color_sep, GIT_COLOR_CYAN);
 	opt.color = -1;
 	git_config(grep_config, &opt);
-	if (opt.color == -1)
-		opt.color = git_use_color_default;
 
 	/*
 	 * If there is no -- then the paths must exist in the working
diff --git a/builtin/log.c b/builtin/log.c
index 5c2af59..d760ee0 100644
--- a/builtin/log.c
+++ b/builtin/log.c
@@ -359,9 +359,6 @@ int cmd_whatchanged(int argc, const char **argv, const char *prefix)
 
 	git_config(git_log_config, NULL);
 
-	if (diff_use_color_default == -1)
-		diff_use_color_default = git_use_color_default;
-
 	init_revisions(&rev, prefix);
 	rev.diff = 1;
 	rev.simplify_history = 0;
@@ -446,9 +443,6 @@ int cmd_show(int argc, const char **argv, const char *prefix)
 
 	git_config(git_log_config, NULL);
 
-	if (diff_use_color_default == -1)
-		diff_use_color_default = git_use_color_default;
-
 	init_pathspec(&match_all, NULL);
 	init_revisions(&rev, prefix);
 	rev.diff = 1;
@@ -524,9 +518,6 @@ int cmd_log_reflog(int argc, const char **argv, const char *prefix)
 
 	git_config(git_log_config, NULL);
 
-	if (diff_use_color_default == -1)
-		diff_use_color_default = git_use_color_default;
-
 	init_revisions(&rev, prefix);
 	init_reflog_walk(&rev.reflog_info);
 	rev.verbose_header = 1;
@@ -549,9 +540,6 @@ int cmd_log(int argc, const char **argv, const char *prefix)
 
 	git_config(git_log_config, NULL);
 
-	if (diff_use_color_default == -1)
-		diff_use_color_default = git_use_color_default;
-
 	init_revisions(&rev, prefix);
 	rev.always_show_header = 1;
 	memset(&opt, 0, sizeof(opt));
diff --git a/builtin/merge.c b/builtin/merge.c
index f32c5c6..ab4077f 100644
--- a/builtin/merge.c
+++ b/builtin/merge.c
@@ -390,8 +390,6 @@ static void finish(const unsigned char *new_head, const char *msg)
 		opts.output_format |=
 			DIFF_FORMAT_SUMMARY | DIFF_FORMAT_DIFFSTAT;
 		opts.detect_rename = DIFF_DETECT_RENAME;
-		if (diff_use_color_default > 0)
-			DIFF_OPT_SET(&opts, COLOR_DIFF);
 		if (diff_setup_done(&opts) < 0)
 			die(_("diff_setup_done failed"));
 		diff_tree_sha1(head, new_head, "", &opts);
@@ -1033,10 +1031,6 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
 
 	git_config(git_merge_config, NULL);
 
-	/* for color.ui */
-	if (diff_use_color_default == -1)
-		diff_use_color_default = git_use_color_default;
-
 	if (branch_mergeoptions)
 		parse_branch_merge_options(branch_mergeoptions);
 	argc = parse_options(argc, argv, prefix, builtin_merge_options,
diff --git a/builtin/show-branch.c b/builtin/show-branch.c
index facc63a..4b480d7 100644
--- a/builtin/show-branch.c
+++ b/builtin/show-branch.c
@@ -26,14 +26,14 @@ static const char **default_arg;
 
 static const char *get_color_code(int idx)
 {
-	if (showbranch_use_color)
+	if (want_color(showbranch_use_color))
 		return column_colors_ansi[idx % column_colors_ansi_max];
 	return "";
 }
 
 static const char *get_color_reset_code(void)
 {
-	if (showbranch_use_color)
+	if (want_color(showbranch_use_color))
 		return GIT_COLOR_RESET;
 	return "";
 }
@@ -573,7 +573,7 @@ static int git_show_branch_config(const char *var, const char *value, void *cb)
 	}
 
 	if (!strcmp(var, "color.showbranch")) {
-		showbranch_use_color = git_config_colorbool(var, value, -1);
+		showbranch_use_color = git_config_colorbool(var, value);
 		return 0;
 	}
 
@@ -685,9 +685,6 @@ int cmd_show_branch(int ac, const char **av, const char *prefix)
 
 	git_config(git_show_branch_config, NULL);
 
-	if (showbranch_use_color == -1)
-		showbranch_use_color = git_use_color_default;
-
 	/* If nothing is specified, try the default first */
 	if (ac == 1 && default_num) {
 		ac = default_num;
diff --git a/color.c b/color.c
index 3db214c..e8e2681 100644
--- a/color.c
+++ b/color.c
@@ -1,7 +1,8 @@
 #include "cache.h"
 #include "color.h"
 
-int git_use_color_default = 0;
+static int git_use_color_default = 0;
+int color_stdout_is_tty = -1;
 
 /*
  * The list of available column colors.
@@ -157,7 +158,7 @@ bad:
 	die("bad color value '%.*s' for variable '%s'", value_len, value, var);
 }
 
-int git_config_colorbool(const char *var, const char *value, int stdout_is_tty)
+int git_config_colorbool(const char *var, const char *value)
 {
 	if (value) {
 		if (!strcasecmp(value, "never"))
@@ -165,7 +166,7 @@ int git_config_colorbool(const char *var, const char *value, int stdout_is_tty)
 		if (!strcasecmp(value, "always"))
 			return 1;
 		if (!strcasecmp(value, "auto"))
-			goto auto_color;
+			return GIT_COLOR_AUTO;
 	}
 
 	if (!var)
@@ -176,10 +177,14 @@ int git_config_colorbool(const char *var, const char *value, int stdout_is_tty)
 		return 0;
 
 	/* any normal truth value defaults to 'auto' */
- auto_color:
-	if (stdout_is_tty < 0)
-		stdout_is_tty = isatty(1);
-	if (stdout_is_tty || (pager_in_use() && pager_use_color)) {
+	return GIT_COLOR_AUTO;
+}
+
+static int check_auto_color(void)
+{
+	if (color_stdout_is_tty < 0)
+		color_stdout_is_tty = isatty(1);
+	if (color_stdout_is_tty || (pager_in_use() && pager_use_color)) {
 		char *term = getenv("TERM");
 		if (term && strcmp(term, "dumb"))
 			return 1;
@@ -187,13 +192,36 @@ int git_config_colorbool(const char *var, const char *value, int stdout_is_tty)
 	return 0;
 }
 
-int git_color_default_config(const char *var, const char *value, void *cb)
+int want_color(int var)
+{
+	static int want_auto = -1;
+
+	if (var < 0)
+		var = git_use_color_default;
+
+	if (var == GIT_COLOR_AUTO) {
+		if (want_auto < 0)
+			want_auto = check_auto_color();
+		return want_auto;
+	}
+	return var;
+}
+
+int git_color_config(const char *var, const char *value, void *cb)
 {
 	if (!strcmp(var, "color.ui")) {
-		git_use_color_default = git_config_colorbool(var, value, -1);
+		git_use_color_default = git_config_colorbool(var, value);
 		return 0;
 	}
 
+	return 0;
+}
+
+int git_color_default_config(const char *var, const char *value, void *cb)
+{
+	if (git_color_config(var, value, cb) < 0)
+		return -1;
+
 	return git_default_config(var, value, cb);
 }
 
diff --git a/color.h b/color.h
index 68a926a..9a8495b 100644
--- a/color.h
+++ b/color.h
@@ -49,20 +49,34 @@ struct strbuf;
 #define GIT_COLOR_NIL "NIL"
 
 /*
- * This variable stores the value of color.ui
+ * The first three are chosen to match common usage in the code, and what is
+ * returned from git_config_colorbool. The "auto" value can be returned from
+ * config_colorbool, and will be converted by want_color() into either 0 or 1.
  */
-extern int git_use_color_default;
+#define GIT_COLOR_UNKNOWN -1
+#define GIT_COLOR_NEVER  0
+#define GIT_COLOR_ALWAYS 1
+#define GIT_COLOR_AUTO   2
 
 /* A default list of colors to use for commit graphs and show-branch output */
 extern const char *column_colors_ansi[];
 extern const int column_colors_ansi_max;
 
 /*
- * Use this instead of git_default_config if you need the value of color.ui.
+ * Generally the color code will lazily figure this out itself, but
+ * this provides a mechanism for callers to override autodetection.
  */
+extern int color_stdout_is_tty;
+
+/*
+ * Use the first one if you need only color config; the second is a convenience
+ * if you are just going to change to git_default_config, too.
+ */
+int git_color_config(const char *var, const char *value, void *cb);
 int git_color_default_config(const char *var, const char *value, void *cb);
 
-int git_config_colorbool(const char *var, const char *value, int stdout_is_tty);
+int git_config_colorbool(const char *var, const char *value);
+int want_color(int var);
 void color_parse(const char *value, const char *var, char *dst);
 void color_parse_mem(const char *value, int len, const char *var, char *dst);
 __attribute__((format (printf, 3, 4)))
diff --git a/combine-diff.c b/combine-diff.c
index 178313b..214014d 100644
--- a/combine-diff.c
+++ b/combine-diff.c
@@ -702,9 +702,8 @@ static void show_combined_header(struct combine_diff_path *elem,
 	int abbrev = DIFF_OPT_TST(opt, FULL_INDEX) ? 40 : DEFAULT_ABBREV;
 	const char *a_prefix = opt->a_prefix ? opt->a_prefix : "a/";
 	const char *b_prefix = opt->b_prefix ? opt->b_prefix : "b/";
-	int use_color = DIFF_OPT_TST(opt, COLOR_DIFF);
-	const char *c_meta = diff_get_color(use_color, DIFF_METAINFO);
-	const char *c_reset = diff_get_color(use_color, DIFF_RESET);
+	const char *c_meta = diff_get_color_opt(opt, DIFF_METAINFO);
+	const char *c_reset = diff_get_color_opt(opt, DIFF_RESET);
 	const char *abb;
 	int added = 0;
 	int deleted = 0;
@@ -964,7 +963,7 @@ static void show_patch_diff(struct combine_diff_path *elem, int num_parent,
 		show_combined_header(elem, num_parent, dense, rev,
 				     mode_differs, 1);
 		dump_sline(sline, cnt, num_parent,
-			   DIFF_OPT_TST(opt, COLOR_DIFF), result_deleted);
+			   opt->use_color, result_deleted);
 	}
 	free(result);
 
diff --git a/diff.c b/diff.c
index d3d8dae..fcc0078 100644
--- a/diff.c
+++ b/diff.c
@@ -137,7 +137,7 @@ static int git_config_rename(const char *var, const char *value)
 int git_diff_ui_config(const char *var, const char *value, void *cb)
 {
 	if (!strcmp(var, "diff.color") || !strcmp(var, "color.diff")) {
-		diff_use_color_default = git_config_colorbool(var, value, -1);
+		diff_use_color_default = git_config_colorbool(var, value);
 		return 0;
 	}
 	if (!strcmp(var, "diff.renames")) {
@@ -164,6 +164,9 @@ int git_diff_ui_config(const char *var, const char *value, void *cb)
 	if (!strcmp(var, "diff.ignoresubmodules"))
 		handle_ignore_submodules_arg(&default_diff_options, value);
 
+	if (git_color_config(var, value, cb) < 0)
+		return -1;
+
 	return git_diff_basic_config(var, value, cb);
 }
 
@@ -212,7 +215,7 @@ int git_diff_basic_config(const char *var, const char *value, void *cb)
 	if (!prefixcmp(var, "submodule."))
 		return parse_submodule_config_option(var, value);
 
-	return git_color_default_config(var, value, cb);
+	return git_default_config(var, value, cb);
 }
 
 static char *quote_two(const char *one, const char *two)
@@ -583,11 +586,10 @@ static void emit_rewrite_diff(const char *name_a,
 			      struct diff_options *o)
 {
 	int lc_a, lc_b;
-	int color_diff = DIFF_OPT_TST(o, COLOR_DIFF);
 	const char *name_a_tab, *name_b_tab;
-	const char *metainfo = diff_get_color(color_diff, DIFF_METAINFO);
-	const char *fraginfo = diff_get_color(color_diff, DIFF_FRAGINFO);
-	const char *reset = diff_get_color(color_diff, DIFF_RESET);
+	const char *metainfo = diff_get_color(o->use_color, DIFF_METAINFO);
+	const char *fraginfo = diff_get_color(o->use_color, DIFF_FRAGINFO);
+	const char *reset = diff_get_color(o->use_color, DIFF_RESET);
 	static struct strbuf a_name = STRBUF_INIT, b_name = STRBUF_INIT;
 	const char *a_prefix, *b_prefix;
 	char *data_one, *data_two;
@@ -623,7 +625,7 @@ static void emit_rewrite_diff(const char *name_a,
 	size_two = fill_textconv(textconv_two, two, &data_two);
 
 	memset(&ecbdata, 0, sizeof(ecbdata));
-	ecbdata.color_diff = color_diff;
+	ecbdata.color_diff = want_color(o->use_color);
 	ecbdata.found_changesp = &o->found_changes;
 	ecbdata.ws_rule = whitespace_rule(name_b ? name_b : name_a);
 	ecbdata.opt = o;
@@ -1004,7 +1006,7 @@ static void free_diff_words_data(struct emit_callback *ecbdata)
 
 const char *diff_get_color(int diff_use_color, enum color_diff ix)
 {
-	if (diff_use_color)
+	if (want_color(diff_use_color))
 		return diff_colors[ix];
 	return "";
 }
@@ -1808,11 +1810,10 @@ static int is_conflict_marker(const char *line, int marker_size, unsigned long l
 static void checkdiff_consume(void *priv, char *line, unsigned long len)
 {
 	struct checkdiff_t *data = priv;
-	int color_diff = DIFF_OPT_TST(data->o, COLOR_DIFF);
 	int marker_size = data->conflict_marker_size;
-	const char *ws = diff_get_color(color_diff, DIFF_WHITESPACE);
-	const char *reset = diff_get_color(color_diff, DIFF_RESET);
-	const char *set = diff_get_color(color_diff, DIFF_FILE_NEW);
+	const char *ws = diff_get_color(data->o->use_color, DIFF_WHITESPACE);
+	const char *reset = diff_get_color(data->o->use_color, DIFF_RESET);
+	const char *set = diff_get_color(data->o->use_color, DIFF_FILE_NEW);
 	char *err;
 	char *line_prefix = "";
 	struct strbuf *msgbuf;
@@ -2157,7 +2158,7 @@ static void builtin_diff(const char *name_a,
 		memset(&xecfg, 0, sizeof(xecfg));
 		memset(&ecbdata, 0, sizeof(ecbdata));
 		ecbdata.label_path = lbl;
-		ecbdata.color_diff = DIFF_OPT_TST(o, COLOR_DIFF);
+		ecbdata.color_diff = want_color(o->use_color);
 		ecbdata.found_changesp = &o->found_changes;
 		ecbdata.ws_rule = whitespace_rule(name_b ? name_b : name_a);
 		if (ecbdata.ws_rule & WS_BLANK_AT_EOF)
@@ -2205,7 +2206,7 @@ static void builtin_diff(const char *name_a,
 					break;
 				}
 			}
-			if (DIFF_OPT_TST(o, COLOR_DIFF)) {
+			if (want_color(o->use_color)) {
 				struct diff_words_style *st = ecbdata.diff_words->style;
 				st->old.color = diff_get_color_opt(o, DIFF_FILE_OLD);
 				st->new.color = diff_get_color_opt(o, DIFF_FILE_NEW);
@@ -2855,7 +2856,7 @@ static void run_diff_cmd(const char *pgm,
 		 */
 		fill_metainfo(msg, name, other, one, two, o, p,
 			      &must_show_header,
-			      DIFF_OPT_TST(o, COLOR_DIFF) && !pgm);
+			      want_color(o->use_color) && !pgm);
 		xfrm_msg = msg->len ? msg->buf : NULL;
 	}
 
@@ -3021,8 +3022,7 @@ void diff_setup(struct diff_options *options)
 
 	options->change = diff_change;
 	options->add_remove = diff_addremove;
-	if (diff_use_color_default > 0)
-		DIFF_OPT_SET(options, COLOR_DIFF);
+	options->use_color = diff_use_color_default;
 	options->detect_rename = diff_detect_rename_default;
 
 	if (diff_no_prefix) {
@@ -3412,24 +3412,21 @@ int diff_opt_parse(struct diff_options *options, const char **av, int ac)
 	else if (!strcmp(arg, "--follow"))
 		DIFF_OPT_SET(options, FOLLOW_RENAMES);
 	else if (!strcmp(arg, "--color"))
-		DIFF_OPT_SET(options, COLOR_DIFF);
+		options->use_color = 1;
 	else if (!prefixcmp(arg, "--color=")) {
-		int value = git_config_colorbool(NULL, arg+8, -1);
-		if (value == 0)
-			DIFF_OPT_CLR(options, COLOR_DIFF);
-		else if (value > 0)
-			DIFF_OPT_SET(options, COLOR_DIFF);
-		else
+		int value = git_config_colorbool(NULL, arg+8);
+		if (value < 0)
 			return error("option `color' expects \"always\", \"auto\", or \"never\"");
+		options->use_color = value;
 	}
 	else if (!strcmp(arg, "--no-color"))
-		DIFF_OPT_CLR(options, COLOR_DIFF);
+		options->use_color = 0;
 	else if (!strcmp(arg, "--color-words")) {
-		DIFF_OPT_SET(options, COLOR_DIFF);
+		options->use_color = 1;
 		options->word_diff = DIFF_WORDS_COLOR;
 	}
 	else if (!prefixcmp(arg, "--color-words=")) {
-		DIFF_OPT_SET(options, COLOR_DIFF);
+		options->use_color = 1;
 		options->word_diff = DIFF_WORDS_COLOR;
 		options->word_regex = arg + 14;
 	}
@@ -3442,7 +3439,7 @@ int diff_opt_parse(struct diff_options *options, const char **av, int ac)
 		if (!strcmp(type, "plain"))
 			options->word_diff = DIFF_WORDS_PLAIN;
 		else if (!strcmp(type, "color")) {
-			DIFF_OPT_SET(options, COLOR_DIFF);
+			options->use_color = 1;
 			options->word_diff = DIFF_WORDS_COLOR;
 		}
 		else if (!strcmp(type, "porcelain"))
diff --git a/diff.h b/diff.h
index b920a20..8c66b59 100644
--- a/diff.h
+++ b/diff.h
@@ -58,7 +58,7 @@ typedef struct strbuf *(*diff_prefix_fn_t)(struct diff_options *opt, void *data)
 #define DIFF_OPT_SILENT_ON_REMOVE    (1 <<  5)
 #define DIFF_OPT_FIND_COPIES_HARDER  (1 <<  6)
 #define DIFF_OPT_FOLLOW_RENAMES      (1 <<  7)
-#define DIFF_OPT_COLOR_DIFF          (1 <<  8)
+/* (1 <<  8) unused */
 /* (1 <<  9) unused */
 #define DIFF_OPT_HAS_CHANGES         (1 << 10)
 #define DIFF_OPT_QUICK               (1 << 11)
@@ -101,6 +101,7 @@ struct diff_options {
 	const char *single_follow;
 	const char *a_prefix, *b_prefix;
 	unsigned flags;
+	int use_color;
 	int context;
 	int interhunkcontext;
 	int break_opt;
@@ -160,7 +161,7 @@ enum color_diff {
 };
 const char *diff_get_color(int diff_use_color, enum color_diff ix);
 #define diff_get_color_opt(o, ix) \
-	diff_get_color(DIFF_OPT_TST((o), COLOR_DIFF), ix)
+	diff_get_color((o)->use_color, ix)
 
 
 extern const char mime_boundary_leader[];
diff --git a/graph.c b/graph.c
index 2f6893d..7358416 100644
--- a/graph.c
+++ b/graph.c
@@ -347,7 +347,7 @@ static struct commit_list *first_interesting_parent(struct git_graph *graph)
 
 static unsigned short graph_get_current_column_color(const struct git_graph *graph)
 {
-	if (!DIFF_OPT_TST(&graph->revs->diffopt, COLOR_DIFF))
+	if (!want_color(graph->revs->diffopt.use_color))
 		return column_colors_max;
 	return graph->default_column_color;
 }
diff --git a/grep.c b/grep.c
index 26e8d8e..2dd2a25 100644
--- a/grep.c
+++ b/grep.c
@@ -430,7 +430,7 @@ static int word_char(char ch)
 static void output_color(struct grep_opt *opt, const void *data, size_t size,
 			 const char *color)
 {
-	if (opt->color && color && color[0]) {
+	if (want_color(opt->color) && color && color[0]) {
 		opt->output(opt, color, strlen(color));
 		opt->output(opt, data, size);
 		opt->output(opt, GIT_COLOR_RESET, strlen(GIT_COLOR_RESET));
diff --git a/log-tree.c b/log-tree.c
index e945701..95d6d40 100644
--- a/log-tree.c
+++ b/log-tree.c
@@ -31,7 +31,7 @@ static char decoration_colors[][COLOR_MAXLEN] = {
 
 static const char *decorate_get_color(int decorate_use_color, enum decoration_type ix)
 {
-	if (decorate_use_color)
+	if (want_color(decorate_use_color))
 		return decoration_colors[ix];
 	return "";
 }
@@ -77,7 +77,7 @@ int parse_decorate_color_config(const char *var, const int ofs, const char *valu
  * for showing the commit sha1, use the same check for --decorate
  */
 #define decorate_get_color_opt(o, ix) \
-	decorate_get_color(DIFF_OPT_TST((o), COLOR_DIFF), ix)
+	decorate_get_color((o)->use_color, ix)
 
 static void add_name_decoration(enum decoration_type type, const char *name, struct object *obj)
 {
diff --git a/pager.c b/pager.c
index dac358f..975955b 100644
--- a/pager.c
+++ b/pager.c
@@ -11,8 +11,6 @@
  * something different on Windows.
  */
 
-static int spawned_pager;
-
 #ifndef WIN32
 static void pager_preexec(void)
 {
@@ -78,7 +76,7 @@ void setup_pager(void)
 	if (!pager)
 		return;
 
-	spawned_pager = 1; /* means we are emitting to terminal */
+	setenv("GIT_PAGER_IN_USE", "true", 1);
 
 	/* spawn the pager */
 	pager_argv[0] = pager;
@@ -109,10 +107,6 @@ void setup_pager(void)
 int pager_in_use(void)
 {
 	const char *env;
-
-	if (spawned_pager)
-		return 1;
-
 	env = getenv("GIT_PAGER_IN_USE");
 	return env ? git_config_bool("GIT_PAGER_IN_USE", env) : 0;
 }
diff --git a/parse-options-cb.c b/parse-options-cb.c
index c248f66..6db0921 100644
--- a/parse-options-cb.c
+++ b/parse-options-cb.c
@@ -40,7 +40,7 @@ int parse_opt_color_flag_cb(const struct option *opt, const char *arg,
 
 	if (!arg)
 		arg = unset ? "never" : (const char *)opt->defval;
-	value = git_config_colorbool(NULL, arg, -1);
+	value = git_config_colorbool(NULL, arg);
 	if (value < 0)
 		return opterror(opt,
 			"expects \"always\", \"auto\", or \"never\"", 0);
diff --git a/t/t7006-pager.sh b/t/t7006-pager.sh
index ed7575d..4582336 100755
--- a/t/t7006-pager.sh
+++ b/t/t7006-pager.sh
@@ -13,7 +13,7 @@ cleanup_fail() {
 
 test_expect_success 'setup' '
 	sane_unset GIT_PAGER GIT_PAGER_IN_USE &&
-	test_might_fail git config --unset core.pager &&
+	test_unconfig core.pager &&
 
 	PAGER="cat >paginated.out" &&
 	export PAGER &&
@@ -94,21 +94,19 @@ test_expect_success TTY 'no pager with --no-pager' '
 
 test_expect_success TTY 'configuration can disable pager' '
 	rm -f paginated.out &&
-	test_might_fail git config --unset pager.grep &&
+	test_unconfig pager.grep &&
 	test_terminal git grep initial &&
 	test -e paginated.out &&
 
 	rm -f paginated.out &&
-	git config pager.grep false &&
-	test_when_finished "git config --unset pager.grep" &&
+	test_config pager.grep false &&
 	test_terminal git grep initial &&
 	! test -e paginated.out
 '
 
 test_expect_success TTY 'git config uses a pager if configured to' '
 	rm -f paginated.out &&
-	git config pager.config true &&
-	test_when_finished "git config --unset pager.config" &&
+	test_config pager.config true &&
 	test_terminal git config --list &&
 	test -e paginated.out
 '
@@ -116,8 +114,7 @@ test_expect_success TTY 'git config uses a pager if configured to' '
 test_expect_success TTY 'configuration can enable pager (from subdir)' '
 	rm -f paginated.out &&
 	mkdir -p subdir &&
-	git config pager.bundle true &&
-	test_when_finished "git config --unset pager.bundle" &&
+	test_config pager.bundle true &&
 
 	git bundle create test.bundle --all &&
 	rm -f paginated.out subdir/paginated.out &&
@@ -150,7 +147,7 @@ test_expect_success 'tests can detect color' '
 
 test_expect_success 'no color when stdout is a regular file' '
 	rm -f colorless.log &&
-	git config color.ui auto ||
+	test_config color.ui auto ||
 	cleanup_fail &&
 
 	git log >colorless.log &&
@@ -159,7 +156,7 @@ test_expect_success 'no color when stdout is a regular file' '
 
 test_expect_success TTY 'color when writing to a pager' '
 	rm -f paginated.out &&
-	git config color.ui auto ||
+	test_config color.ui auto ||
 	cleanup_fail &&
 
 	(
@@ -170,9 +167,21 @@ test_expect_success TTY 'color when writing to a pager' '
 	colorful paginated.out
 '
 
+test_expect_success TTY 'colors are suppressed by color.pager' '
+	rm -f paginated.out &&
+	test_config color.ui auto &&
+	test_config color.pager false &&
+	(
+		TERM=vt100 &&
+		export TERM &&
+		test_terminal git log
+	) &&
+	! colorful paginated.out
+'
+
 test_expect_success 'color when writing to a file intended for a pager' '
 	rm -f colorful.log &&
-	git config color.ui auto ||
+	test_config color.ui auto ||
 	cleanup_fail &&
 
 	(
@@ -184,6 +193,17 @@ test_expect_success 'color when writing to a file intended for a pager' '
 	colorful colorful.log
 '
 
+test_expect_success TTY 'colors are sent to pager for external commands' '
+	test_config alias.externallog "!git log" &&
+	test_config color.ui auto &&
+	(
+		TERM=vt100 &&
+		export TERM &&
+		test_terminal git -p externallog
+	) &&
+	colorful paginated.out
+'
+
 # Use this helper to make it easy for the caller of your
 # terminal-using function to specify whether it should fail.
 # If you write
@@ -221,7 +241,7 @@ test_default_pager() {
 
 	$test_expectation SIMPLEPAGER,TTY "$cmd - default pager is used by default" "
 		sane_unset PAGER GIT_PAGER &&
-		test_might_fail git config --unset core.pager &&
+		test_unconfig core.pager &&
 		rm -f default_pager_used ||
 		cleanup_fail &&
 
@@ -244,7 +264,7 @@ test_PAGER_overrides() {
 
 	$test_expectation TTY "$cmd - PAGER overrides default pager" "
 		sane_unset GIT_PAGER &&
-		test_might_fail git config --unset core.pager &&
+		test_unconfig core.pager &&
 		rm -f PAGER_used ||
 		cleanup_fail &&
 
@@ -277,7 +297,7 @@ test_core_pager() {
 
 		PAGER=wc &&
 		export PAGER &&
-		git config core.pager 'wc >core.pager_used' &&
+		test_config core.pager 'wc >core.pager_used' &&
 		$full_command &&
 		${if_local_config}test -e core.pager_used
 	"
@@ -307,7 +327,7 @@ test_pager_subdir_helper() {
 		PAGER=wc &&
 		stampname=\$(pwd)/core.pager_used &&
 		export PAGER stampname &&
-		git config core.pager 'wc >\"\$stampname\"' &&
+		test_config core.pager 'wc >\"\$stampname\"' &&
 		mkdir sub &&
 		(
 			cd sub &&
@@ -324,7 +344,7 @@ test_GIT_PAGER_overrides() {
 		rm -f GIT_PAGER_used ||
 		cleanup_fail &&
 
-		git config core.pager wc &&
+		test_config core.pager wc &&
 		GIT_PAGER='wc >GIT_PAGER_used' &&
 		export GIT_PAGER &&
 		$full_command &&
@@ -402,21 +422,21 @@ test_core_pager_subdir    expect_success test_must_fail \
 					 'git -p apply </dev/null'
 
 test_expect_success TTY 'command-specific pager' '
-	unset PAGER GIT_PAGER;
+	sane_unset PAGER GIT_PAGER &&
 	echo "foo:initial" >expect &&
 	>actual &&
-	git config --unset core.pager &&
-	git config pager.log "sed s/^/foo:/ >actual" &&
+	test_unconfig core.pager &&
+	test_config pager.log "sed s/^/foo:/ >actual" &&
 	test_terminal git log --format=%s -1 &&
 	test_cmp expect actual
 '
 
 test_expect_success TTY 'command-specific pager overrides core.pager' '
-	unset PAGER GIT_PAGER;
+	sane_unset PAGER GIT_PAGER &&
 	echo "foo:initial" >expect &&
 	>actual &&
-	git config core.pager "exit 1"
-	git config pager.log "sed s/^/foo:/ >actual" &&
+	test_config core.pager "exit 1"
+	test_config pager.log "sed s/^/foo:/ >actual" &&
 	test_terminal git log --format=%s -1 &&
 	test_cmp expect actual
 '
@@ -425,7 +445,7 @@ test_expect_success TTY 'command-specific pager overridden by environment' '
 	GIT_PAGER="sed s/^/foo:/ >actual" && export GIT_PAGER &&
 	>actual &&
 	echo "foo:initial" >expect &&
-	git config pager.log "exit 1" &&
+	test_config pager.log "exit 1" &&
 	test_terminal git log --format=%s -1 &&
 	test_cmp expect actual
 '
diff --git a/t/test-lib.sh b/t/test-lib.sh
index e274222..d7dfc8b 100644
--- a/t/test-lib.sh
+++ b/t/test-lib.sh
@@ -361,6 +361,24 @@ test_chmod () {
 	git update-index --add "--chmod=$@"
 }
 
+# Unset a configuration variable, but don't fail if it doesn't exist.
+test_unconfig () {
+	git config --unset-all "$@"
+	config_status=$?
+	case "$config_status" in
+	5) # ok, nothing to unset
+		config_status=0
+		;;
+	esac
+	return $config_status
+}
+
+# Set git config, automatically unsetting it after the test is over.
+test_config () {
+	test_when_finished "test_unconfig '$1'" &&
+	git config "$@"
+}
+
 # Use test_set_prereq to tell that a particular prerequisite is available.
 # The prerequisite can later be checked for in two ways:
 #
diff --git a/wt-status.c b/wt-status.c
index 0237772..8836a52 100644
--- a/wt-status.c
+++ b/wt-status.c
@@ -26,7 +26,9 @@ static char default_wt_status_colors[][COLOR_MAXLEN] = {
 
 static const char *color(int slot, struct wt_status *s)
 {
-	const char *c = s->use_color > 0 ? s->color_palette[slot] : "";
+	const char *c = "";
+	if (want_color(s->use_color))
+		c = s->color_palette[slot];
 	if (slot == WT_STATUS_ONBRANCH && color_is_nil(c))
 		c = s->color_palette[WT_STATUS_HEADER];
 	return c;
@@ -681,7 +683,7 @@ static void wt_status_print_verbose(struct wt_status *s)
 	 * will have checked isatty on stdout).
 	 */
 	if (s->fp != stdout)
-		DIFF_OPT_CLR(&rev.diffopt, COLOR_DIFF);
+		rev.diffopt.use_color = 0;
 	run_diff_index(&rev, 1);
 }