Merge branch 'ma/pager-per-subcommand-action' into maint

The "tag.pager" configuration variable was useless for those who
actually create tag objects, as it interfered with the use of an
editor.  A new mechanism has been introduced for commands to enable
pager depending on what operation is being carried out to fix this,
and then "git tag -l" is made to run pager by default.

If this works out OK, I think there are low-hanging fruits in
other commands like "git branch" that outputs long list in one mode
while taking input in another.

* ma/pager-per-subcommand-action:
  git.c: ignore pager.* when launching builtin as dashed external
  tag: change default of `pager.tag` to "on"
  tag: respect `pager.tag` in list-mode only
  t7006: add tests for how git tag paginates
  git.c: provide setup_auto_pager()
  git.c: let builtins opt for handling `pager.foo` themselves
  builtin.h: take over documentation from api-builtin.txt

Documentation/git-tag.txt

@@ -205,6 +205,9 @@ it in the repository configuration as follows:
     signingKey = <gpg-keyid>
 -------------------------------------
 
+`pager.tag` is only respected when listing tags, i.e., when `-l` is
+used or implied. The default is to use a pager.
+See linkgit:git-config[1].
 
 DISCUSSION
 ----------

Documentation/technical/api-builtin.txt

@@ -1,73 +0,0 @@
-builtin API
-===========
-
-Adding a new built-in
----------------------
-
-There are 4 things to do to add a built-in command implementation to
-Git:
-
-. Define the implementation of the built-in command `foo` with
-  signature:
-
-	int cmd_foo(int argc, const char **argv, const char *prefix);
-
-. Add the external declaration for the function to `builtin.h`.
-
-. Add the command to the `commands[]` table defined in `git.c`.
-  The entry should look like:
-
-	{ "foo", cmd_foo, <options> },
-+
-where options is the bitwise-or of:
-
-`RUN_SETUP`::
-	If there is not a Git directory to work on, abort.  If there
-	is a work tree, chdir to the top of it if the command was
-	invoked in a subdirectory.  If there is no work tree, no
-	chdir() is done.
-
-`RUN_SETUP_GENTLY`::
-	If there is a Git directory, chdir as per RUN_SETUP, otherwise,
-	don't chdir anywhere.
-
-`USE_PAGER`::
-
-	If the standard output is connected to a tty, spawn a pager and
-	feed our output to it.
-
-`NEED_WORK_TREE`::
-
-	Make sure there is a work tree, i.e. the command cannot act
-	on bare repositories.
-	This only makes sense when `RUN_SETUP` is also set.
-
-. Add `builtin/foo.o` to `BUILTIN_OBJS` in `Makefile`.
-
-Additionally, if `foo` is a new command, there are 3 more things to do:
-
-. Add tests to `t/` directory.
-
-. Write documentation in `Documentation/git-foo.txt`.
-
-. Add an entry for `git-foo` to `command-list.txt`.
-
-. Add an entry for `/git-foo` to `.gitignore`.
-
-
-How a built-in is called
-------------------------
-
-The implementation `cmd_foo()` takes three parameters, `argc`, `argv,
-and `prefix`.  The first two are similar to what `main()` of a
-standalone command would be called with.
-
-When `RUN_SETUP` is specified in the `commands[]` table, and when you
-were started from a subdirectory of the work tree, `cmd_foo()` is called
-after chdir(2) to the top of the work tree, and `prefix` gets the path
-to the subdirectory the command started from.  This allows you to
-convert a user-supplied pathname (typically relative to that directory)
-to a pathname relative to the top of the work tree.
-
-The return value from `cmd_foo()` becomes the exit status of the
-command.

builtin.h

@@ -6,6 +6,94 @@
 #include "cache.h"
 #include "commit.h"
 
+/*
+ * builtin API
+ * ===========
+ *
+ * Adding a new built-in
+ * ---------------------
+ *
+ * There are 4 things to do to add a built-in command implementation to
+ * Git:
+ *
+ * . Define the implementation of the built-in command `foo` with
+ *   signature:
+ *
+ *	int cmd_foo(int argc, const char **argv, const char *prefix);
+ *
+ * . Add the external declaration for the function to `builtin.h`.
+ *
+ * . Add the command to the `commands[]` table defined in `git.c`.
+ *   The entry should look like:
+ *
+ *	{ "foo", cmd_foo, <options> },
+ *
+ * where options is the bitwise-or of:
+ *
+ * `RUN_SETUP`:
+ *	If there is not a Git directory to work on, abort.  If there
+ *	is a work tree, chdir to the top of it if the command was
+ *	invoked in a subdirectory.  If there is no work tree, no
+ *	chdir() is done.
+ *
+ * `RUN_SETUP_GENTLY`:
+ *	If there is a Git directory, chdir as per RUN_SETUP, otherwise,
+ *	don't chdir anywhere.
+ *
+ * `USE_PAGER`:
+ *
+ *	If the standard output is connected to a tty, spawn a pager and
+ *	feed our output to it.
+ *
+ * `NEED_WORK_TREE`:
+ *
+ *	Make sure there is a work tree, i.e. the command cannot act
+ *	on bare repositories.
+ *	This only makes sense when `RUN_SETUP` is also set.
+ *
+ * `SUPPORT_SUPER_PREFIX`:
+ *
+ *	The built-in supports `--super-prefix`.
+ *
+ * `DELAY_PAGER_CONFIG`:
+ *
+ *	If RUN_SETUP or RUN_SETUP_GENTLY is set, git.c normally handles
+ *	the `pager.<cmd>`-configuration. If this flag is used, git.c
+ *	will skip that step, instead allowing the built-in to make a
+ *	more informed decision, e.g., by ignoring `pager.<cmd>` for
+ *	certain subcommands.
+ *
+ * . Add `builtin/foo.o` to `BUILTIN_OBJS` in `Makefile`.
+ *
+ * Additionally, if `foo` is a new command, there are 4 more things to do:
+ *
+ * . Add tests to `t/` directory.
+ *
+ * . Write documentation in `Documentation/git-foo.txt`.
+ *
+ * . Add an entry for `git-foo` to `command-list.txt`.
+ *
+ * . Add an entry for `/git-foo` to `.gitignore`.
+ *
+ *
+ * How a built-in is called
+ * ------------------------
+ *
+ * The implementation `cmd_foo()` takes three parameters, `argc`, `argv,
+ * and `prefix`.  The first two are similar to what `main()` of a
+ * standalone command would be called with.
+ *
+ * When `RUN_SETUP` is specified in the `commands[]` table, and when you
+ * were started from a subdirectory of the work tree, `cmd_foo()` is called
+ * after chdir(2) to the top of the work tree, and `prefix` gets the path
+ * to the subdirectory the command started from.  This allows you to
+ * convert a user-supplied pathname (typically relative to that directory)
+ * to a pathname relative to the top of the work tree.
+ *
+ * The return value from `cmd_foo()` becomes the exit status of the
+ * command.
+ */
+
 #define DEFAULT_MERGE_LOG_LEN 20
 
 extern const char git_usage_string[];
@@ -25,6 +113,18 @@ struct fmt_merge_msg_opts {
 extern int fmt_merge_msg(struct strbuf *in, struct strbuf *out,
 			 struct fmt_merge_msg_opts *);
 
+/**
+ * If a built-in has DELAY_PAGER_CONFIG set, the built-in should call this early
+ * when it wishes to respect the `pager.foo`-config. The `cmd` is the name of
+ * the built-in, e.g., "foo". If a paging-choice has already been setup, this
+ * does nothing. The default in `def` should be 0 for "pager off", 1 for "pager
+ * on" or -1 for "punt".
+ *
+ * You should most likely use a default of 0 or 1. "Punt" (-1) could be useful
+ * to be able to fall back to some historical compatibility name.
+ */
+extern void setup_auto_pager(const char *cmd, int def);
+
 extern int is_builtin(const char *s);
 
 extern int cmd_add(int argc, const char **argv, const char *prefix);

builtin/tag.c

@@ -440,6 +440,9 @@ int cmd_tag(int argc, const char **argv, const char *prefix)
 			cmdmode = 'l';
 	}
 
+	if (cmdmode == 'l')
+		setup_auto_pager("tag", 1);
+
 	if ((create_tag_object || force) && (cmdmode != 0))
 		usage_with_options(git_tag_usage, options);
 

git.c

@@ -33,6 +33,16 @@ static void commit_pager_choice(void) {
 	}
 }
 
+void setup_auto_pager(const char *cmd, int def)
+{
+	if (use_pager != -1 || pager_in_use())
+		return;
+	use_pager = check_pager_config(cmd);
+	if (use_pager == -1)
+		use_pager = def;
+	commit_pager_choice();
+}
+
 static int handle_options(const char ***argv, int *argc, int *envchanged)
 {
 	const char **orig_argv = *argv;
@@ -283,6 +293,7 @@ static int handle_alias(int *argcp, const char ***argv)
  */
 #define NEED_WORK_TREE		(1<<3)
 #define SUPPORT_SUPER_PREFIX	(1<<4)
+#define DELAY_PAGER_CONFIG	(1<<5)
 
 struct cmd_struct {
 	const char *cmd;
@@ -306,7 +317,8 @@ static int run_builtin(struct cmd_struct *p, int argc, const char **argv)
 			prefix = setup_git_directory_gently(&nongit_ok);
 		}
 
-		if (use_pager == -1 && p->option & (RUN_SETUP | RUN_SETUP_GENTLY))
+		if (use_pager == -1 && p->option & (RUN_SETUP | RUN_SETUP_GENTLY) &&
+		    !(p->option & DELAY_PAGER_CONFIG))
 			use_pager = check_pager_config(p->cmd);
 		if (use_pager == -1 && p->option & USE_PAGER)
 			use_pager = 1;
@@ -454,7 +466,7 @@ static struct cmd_struct commands[] = {
 	{ "stripspace", cmd_stripspace },
 	{ "submodule--helper", cmd_submodule__helper, RUN_SETUP | SUPPORT_SUPER_PREFIX},
 	{ "symbolic-ref", cmd_symbolic_ref, RUN_SETUP },
-	{ "tag", cmd_tag, RUN_SETUP },
+	{ "tag", cmd_tag, RUN_SETUP | DELAY_PAGER_CONFIG },
 	{ "unpack-file", cmd_unpack_file, RUN_SETUP },
 	{ "unpack-objects", cmd_unpack_objects, RUN_SETUP },
 	{ "update-index", cmd_update_index, RUN_SETUP },
@@ -547,7 +559,7 @@ static void execv_dashed_external(const char **argv)
 	if (get_super_prefix())
 		die("%s doesn't support --super-prefix", argv[0]);
 
-	if (use_pager == -1)
+	if (use_pager == -1 && !is_builtin(argv[0]))
 		use_pager = check_pager_config(argv[0]);
 	commit_pager_choice();
 

t/t7006-pager.sh

@@ -134,6 +134,86 @@ test_expect_success TTY 'configuration can enable pager (from subdir)' '
 	}
 '
 
+test_expect_success TTY 'git tag -l defaults to paging' '
+	rm -f paginated.out &&
+	test_terminal git tag -l &&
+	test -e paginated.out
+'
+
+test_expect_success TTY 'git tag -l respects pager.tag' '
+	rm -f paginated.out &&
+	test_terminal git -c pager.tag=false tag -l &&
+	! test -e paginated.out
+'
+
+test_expect_success TTY 'git tag -l respects --no-pager' '
+	rm -f paginated.out &&
+	test_terminal git -c pager.tag --no-pager tag -l &&
+	! test -e paginated.out
+'
+
+test_expect_success TTY 'git tag with no args defaults to paging' '
+	# no args implies -l so this should page like -l
+	rm -f paginated.out &&
+	test_terminal git tag &&
+	test -e paginated.out
+'
+
+test_expect_success TTY 'git tag with no args respects pager.tag' '
+	# no args implies -l so this should page like -l
+	rm -f paginated.out &&
+	test_terminal git -c pager.tag=false tag &&
+	! test -e paginated.out
+'
+
+test_expect_success TTY 'git tag --contains defaults to paging' '
+	# --contains implies -l so this should page like -l
+	rm -f paginated.out &&
+	test_terminal git tag --contains &&
+	test -e paginated.out
+'
+
+test_expect_success TTY 'git tag --contains respects pager.tag' '
+	# --contains implies -l so this should page like -l
+	rm -f paginated.out &&
+	test_terminal git -c pager.tag=false tag --contains &&
+	! test -e paginated.out
+'
+
+test_expect_success TTY 'git tag -a defaults to not paging' '
+	test_when_finished "git tag -d newtag" &&
+	rm -f paginated.out &&
+	test_terminal git tag -am message newtag &&
+	! test -e paginated.out
+'
+
+test_expect_success TTY 'git tag -a ignores pager.tag' '
+	test_when_finished "git tag -d newtag" &&
+	rm -f paginated.out &&
+	test_terminal git -c pager.tag tag -am message newtag &&
+	! test -e paginated.out
+'
+
+test_expect_success TTY 'git tag -a respects --paginate' '
+	test_when_finished "git tag -d newtag" &&
+	rm -f paginated.out &&
+	test_terminal git --paginate tag -am message newtag &&
+	test -e paginated.out
+'
+
+test_expect_success TTY 'git tag as alias ignores pager.tag with -a' '
+	test_when_finished "git tag -d newtag" &&
+	rm -f paginated.out &&
+	test_terminal git -c pager.tag -c alias.t=tag t -am message newtag &&
+	! test -e paginated.out
+'
+
+test_expect_success TTY 'git tag as alias respects pager.tag with -l' '
+	rm -f paginated.out &&
+	test_terminal git -c pager.tag=false -c alias.t=tag t -l &&
+	! test -e paginated.out
+'
+
 # A colored commit log will begin with an appropriate ANSI escape
 # for the first color; the text "commit" comes later.
 colorful() {