Move setup_diff_pager to libgit.a

This is used by diff-no-index.c, part of libgit.a while it stays in
builtin/diff.c. Move it to diff.c so that we won't get undefined
reference if a program that uses libgit.a happens to pull it in.

While at it, move check_pager from git.c to pager.c. It makes more
sense there and pager.c is also part of libgit.a

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Jeff King <peff@peff.net>

builtin.h

@@ -37,10 +37,6 @@ int copy_note_for_rewrite(struct notes_rewrite_cfg *c,
 			  const unsigned char *from_obj, const unsigned char *to_obj);
 void finish_copy_notes_for_rewrite(struct notes_rewrite_cfg *c);
 
-extern int check_pager_config(const char *cmd);
-struct diff_options;
-extern void setup_diff_pager(struct diff_options *);
-
 extern int textconv_object(const char *path, unsigned mode, const unsigned char *sha1, int sha1_valid, char **buf, unsigned long *buf_size);
 
 extern int cmd_add(int argc, const char **argv, const char *prefix);

builtin/diff.c

@@ -418,19 +418,3 @@ int cmd_diff(int argc, const char **argv, const char *prefix)
 		refresh_index_quietly();
 	return result;
 }
-
-void setup_diff_pager(struct diff_options *opt)
-{
-	/*
-	 * If the user asked for our exit code, then either they want --quiet
-	 * or --exit-code. We should definitely not bother with a pager in the
-	 * former case, as we will generate no output. Since we still properly
-	 * report our exit code even when a pager is run, we _could_ run a
-	 * pager with --exit-code. But since we have not done so historically,
-	 * and because it is easy to find people oneline advising "git diff
-	 * --exit-code" in hooks and other scripts, we do not do so.
-	 */
-	if (!DIFF_OPT_TST(opt, EXIT_WITH_STATUS) &&
-	    check_pager_config("diff") != 0)
-		setup_pager();
-}

cache.h

@@ -1183,6 +1183,7 @@ extern int pager_in_use(void);
 extern int pager_use_color;
 extern int term_columns(void);
 extern int decimal_width(int);
+extern int check_pager_config(const char *cmd);
 
 extern const char *editor_program;
 extern const char *askpass_program;

diff.c

@@ -4878,3 +4878,19 @@ size_t fill_textconv(struct userdiff_driver *driver,
 
 	return size;
 }
+
+void setup_diff_pager(struct diff_options *opt)
+{
+	/*
+	 * If the user asked for our exit code, then either they want --quiet
+	 * or --exit-code. We should definitely not bother with a pager in the
+	 * former case, as we will generate no output. Since we still properly
+	 * report our exit code even when a pager is run, we _could_ run a
+	 * pager with --exit-code. But since we have not done so historically,
+	 * and because it is easy to find people oneline advising "git diff
+	 * --exit-code" in hooks and other scripts, we do not do so.
+	 */
+	if (!DIFF_OPT_TST(opt, EXIT_WITH_STATUS) &&
+	    check_pager_config("diff") != 0)
+		setup_pager();
+}

diff.h

@@ -335,5 +335,6 @@ extern int parse_rename_score(const char **cp_p);
 
 extern int print_stat_summary(FILE *fp, int files,
 			      int insertions, int deletions);
+extern void setup_diff_pager(struct diff_options *);
 
 #endif /* DIFF_H */

git.c

@@ -17,39 +17,6 @@ const char git_more_info_string[] =
 
 static struct startup_info git_startup_info;
 static int use_pager = -1;
-struct pager_config {
-	const char *cmd;
-	int want;
-	char *value;
-};
-
-static int pager_command_config(const char *var, const char *value, void *data)
-{
-	struct pager_config *c = data;
-	if (!prefixcmp(var, "pager.") && !strcmp(var + 6, c->cmd)) {
-		int b = git_config_maybe_bool(var, value);
-		if (b >= 0)
-			c->want = b;
-		else {
-			c->want = 1;
-			c->value = xstrdup(value);
-		}
-	}
-	return 0;
-}
-
-/* returns 0 for "no pager", 1 for "use pager", and -1 for "not specified" */
-int check_pager_config(const char *cmd)
-{
-	struct pager_config c;
-	c.cmd = cmd;
-	c.want = -1;
-	c.value = NULL;
-	git_config(pager_command_config, &c);
-	if (c.value)
-		pager_program = c.value;
-	return c.want;
-}
 
 static void commit_pager_choice(void) {
 	switch (use_pager) {

pager.c

@@ -6,6 +6,12 @@
 #define DEFAULT_PAGER "less"
 #endif
 
+struct pager_config {
+	const char *cmd;
+	int want;
+	char *value;
+};
+
 /*
  * This is split up from the rest of git so that we can do
  * something different on Windows.
@@ -141,3 +147,31 @@ int decimal_width(int number)
 		i *= 10;
 	return width;
 }
+
+static int pager_command_config(const char *var, const char *value, void *data)
+{
+	struct pager_config *c = data;
+	if (!prefixcmp(var, "pager.") && !strcmp(var + 6, c->cmd)) {
+		int b = git_config_maybe_bool(var, value);
+		if (b >= 0)
+			c->want = b;
+		else {
+			c->want = 1;
+			c->value = xstrdup(value);
+		}
+	}
+	return 0;
+}
+
+/* returns 0 for "no pager", 1 for "use pager", and -1 for "not specified" */
+int check_pager_config(const char *cmd)
+{
+	struct pager_config c;
+	c.cmd = cmd;
+	c.want = -1;
+	c.value = NULL;
+	git_config(pager_command_config, &c);
+	if (c.value)
+		pager_program = c.value;
+	return c.want;
+}