hooks: add custom post-command hook config

Documentation/config.adoc

@@ -490,6 +490,8 @@ include::config/pack.adoc[]
 
 include::config/pager.adoc[]
 
+include::config/postcommand.adoc[]
+
 include::config/pretty.adoc[]
 
 include::config/promisor.adoc[]

Documentation/config/postcommand.adoc

@@ -0,0 +1,13 @@
+postCommand.strategy::
+	The `post-command` hook is run on every Git process by default. This
+	config option allows running the hook only conditionally, according
+	to these values:
++
+----
+`always`;;
+	run the `post-command` hook on every process (default).
+
+`post-index-change`;;
+	run the `post-command` hook only if the current process wrote to
+	the index.
+----

Documentation/config/protocol.adoc

@@ -6,7 +6,7 @@ protocol.allow::
 	default policy of `never`, and all other protocols (including file)
 	have a default policy of `user`.  Supported policies:
 +
---
+----
 
 * `always` - protocol is always able to be used.
 
@@ -18,15 +18,15 @@ protocol.allow::
   execute clone/fetch/push commands without user input, e.g. recursive
   submodule initialization.
 
---
+----
 
 protocol.<name>.allow::
 	Set a policy to be used by protocol `<name>` with clone/fetch/push
 	commands. See `protocol.allow` above for the available policies.
 +
 The protocol names currently used by git are:
 +
---
+----
   - `file`: any local file-based path (including `file://` URLs,
     or local paths)
 
@@ -42,7 +42,7 @@ The protocol names currently used by git are:
 
   - any external helpers are named by their protocol (e.g., use
     `hg` to allow the `git-remote-hg` helper)
---
+----
 
 protocol.version::
 	If set, clients will attempt to communicate with a server
@@ -51,7 +51,7 @@ protocol.version::
 	If unset, the default is `2`.
 	Supported versions:
 +
---
+----
 
 * `0` - the original wire protocol.
 
@@ -60,4 +60,4 @@ protocol.version::
 
 * `2` - Wire protocol version 2, see linkgit:gitprotocol-v2[5].
 
---
+----

Documentation/config/push.adoc

@@ -17,7 +17,7 @@ push.default::
 	(i.e. the fetch source is equal to the push destination),
 	`upstream` is probably what you want.  Possible values are:
 +
---
+----
 
 * `nothing` - do not push anything (error out) unless a refspec is
   given. This is primarily meant for people who want to
@@ -64,7 +64,7 @@ branches outside your control.
 This used to be the default, but not since Git 2.0 (`simple` is the
 new default).
 
---
+----
 
 push.followTags::
 	If set to true, enable `--follow-tags` option by default.  You

Documentation/config/sendemail.adoc

@@ -58,7 +58,7 @@ the documentation of the email program of the same name. The
 differences and limitations from the standard formats are
 described below:
 +
---
+----
 sendmail;;
 *	Quoted aliases and quoted addresses are not supported: lines that
 	contain a `"` symbol are ignored.
@@ -68,7 +68,7 @@ sendmail;;
 *	Warnings are printed on the standard error output for any
 	explicitly unsupported constructs, and any other lines that are not
 	recognized by the parser.
---
+----
 sendemail.annotate::
 sendemail.bcc::
 sendemail.cc::

Documentation/config/sideband.adoc

@@ -4,7 +4,7 @@ sideband.allowControlCharacters::
 	unwanted ANSI escape sequences from being sent to the terminal. Use
 	this config setting to override this behavior:
 +
---
+----
 	color::
 		Allow ANSI color sequences, line feeds and horizontal tabs,
 		but mask all other control characters. This is the default.
@@ -13,4 +13,4 @@ sideband.allowControlCharacters::
 		horizontal tabs.
 	true::
 		Allow all control characters to be sent to the terminal.
---
+----

Documentation/config/ssh.adoc

@@ -19,7 +19,7 @@ overridden via the environment variable `GIT_SSH_VARIANT`.
 The current command-line parameters used for each variant are as
 follows:
 +
---
+----
 
 * `ssh` - [-p port] [-4] [-6] [-o option] [username@]host command
 
@@ -29,7 +29,7 @@ follows:
 
 * `tortoiseplink` - [-P port] [-4] [-6] -batch [username@]host command
 
---
+----
 +
 Except for the `simple` variant, command-line parameters are likely to
 change as git gains new features.

Documentation/config/status.adoc

@@ -50,11 +50,11 @@ status.showUntrackedFiles::
 	systems. So, this variable controls how the commands display
 	the untracked files. Possible values are:
 +
---
+----
 * `no` - Show no untracked files.
 * `normal` - Show untracked files and directories.
 * `all` - Show also individual files in untracked directories.
---
+----
 +
 If this variable is not specified, it defaults to 'normal'.
 All usual spellings for Boolean value `true` are taken as `normal`
@@ -90,12 +90,12 @@ status.deserializeWait::
 	fall-back and compute status normally.  This will be overridden by
 	`--deserialize-wait=<value>` on the command line.
 +
---
+----
 * `fail` - cause git to exit with an error when the status cache file
 is stale; this is intended for testing and debugging.
 * `block` - cause git to spin and periodically retry the cache file
 every 100 ms; this is intended to help coordinate with another git
 instance concurrently computing the cache file.
 * `no` - to immediately fall-back if cache file is stale.  This is the default.
 * `<timeout>` - time (in tenths of a second) to spin and retry.
---
+----

Documentation/config/survey.adoc

@@ -3,7 +3,7 @@ survey.*::
 	command. The intention is that this command could be run in the
 	background with these options.
 +
---
+----
 	survey.namerev::
 		Boolean to show/hide `git name-rev` information for each
 		reported commit and the containing commit of each
@@ -44,4 +44,4 @@ survey.*::
 		long file or subdirectory entry names.  Provides a
 		default value for `--tree-sizes=<n>` in
 		linkgit:git-survey[1].
---
+----

Documentation/config/trace2.adoc

@@ -16,7 +16,7 @@ trace2.eventTarget::
 	This variable controls the event target destination.
 	It may be overridden by the `GIT_TRACE2_EVENT` environment variable.
 	The following table shows possible values.
-+
+
 include::../trace2-target-values.adoc[]
 
 trace2.normalBrief::

Documentation/trace2-target-values.adoc

@@ -1,12 +1,12 @@
---
+----
 * `0` or `false` - Disables the target.
 * `1` or `true` - Writes to `STDERR`.
 * `[2-9]` - Writes to the already opened file descriptor.
 * `<absolute-pathname>` - Writes to the file in append mode. If the target
-already exists and is a directory, the traces will be written to files (one
-per process) underneath the given directory.
+  already exists and is a directory, the traces will be written to files (one
+  per process) underneath the given directory.
 * `af_unix:[<socket-type>:]<absolute-pathname>` - Write to a
-Unix DomainSocket (on platforms that support them).  Socket
-type can be either `stream` or `dgram`; if omitted Git will
-try both.
---
+  Unix DomainSocket (on platforms that support them).  Socket
+  type can be either `stream` or `dgram`; if omitted Git will
+  try both.
+----

git.c

@@ -494,6 +494,7 @@ static int run_post_command_hook(struct repository *r)
 
 	run_post_hook = 0;
 	strvec_clear(&sargv);
+	strvec_clear(&opt.args);
 	setenv("COMMAND_HOOK_LOCK", "false", 1);
 	return ret;
 }

hook.c

@@ -1,6 +1,7 @@
 #define USE_THE_REPOSITORY_VARIABLE
 
 #include "git-compat-util.h"
+#include "trace2/tr2_sid.h"
 #include "abspath.h"
 #include "environment.h"
 #include "advice.h"
@@ -176,6 +177,58 @@ static void run_hooks_opt_clear(struct run_hooks_opt *options)
 	strvec_clear(&options->args);
 }
 
+static char *get_post_index_change_sentinel_name(struct repository *r)
+{
+	struct strbuf path = STRBUF_INIT;
+	const char *sid = tr2_sid_get();
+	char *slash = strchr(sid, '/');
+
+	/*
+	 * Name is based on top-level SID, so children can indicate that
+	 * the top-level process should run the post-command hook.
+	 */
+	if (slash)
+		*slash = 0;
+
+	repo_git_path_replace(r, &path, "hooks/index-change-%s.snt", sid);
+
+	return strbuf_detach(&path, NULL);
+}
+
+static int write_post_index_change_sentinel(struct repository *r)
+{
+	char *path = get_post_index_change_sentinel_name(r);
+	FILE *fp = xfopen(path, "w");
+
+	if (fp) {
+		fprintf(fp, "run post-command hook");
+		fclose(fp);
+	}
+
+	free(path);
+	return fp ? 0 : -1;
+}
+
+/**
+ * Try to delete the sentinel file for this repository. If that succeeds, then
+ * return 1.
+ */
+static int post_index_change_sentinel_exists(struct repository *r)
+{
+	char *path = get_post_index_change_sentinel_name(r);
+	int res = 1;
+
+	if (unlink(path)) {
+		if (is_missing_file_error(errno))
+			res = 0;
+		else
+			warning_errno("failed to remove index-change sentinel file '%s'", path);
+	}
+
+	free(path);
+	return res;
+}
+
 int run_hooks_opt(struct repository *r, const char *hook_name,
 		  struct run_hooks_opt *options)
 {
@@ -185,7 +238,7 @@ int run_hooks_opt(struct repository *r, const char *hook_name,
 		.hook_name = hook_name,
 		.options = options,
 	};
-	const char *hook_path = find_hook(r, hook_name);
+	const char *hook_path;
 	int ret = 0;
 	const struct run_process_parallel_opts opts = {
 		.tr2_category = "hook",
@@ -201,6 +254,21 @@ int run_hooks_opt(struct repository *r, const char *hook_name,
 		.data = &cb_data,
 	};
 
+	/* Interject hook behavior depending on strategy. */
+	if (r && r->gitdir) {
+		const char *strval;
+		if (!repo_config_get_string_tmp(r, "postcommand.strategy", &strval) &&
+		    !strcasecmp(strval, "post-index-change")) {
+			if (!strcmp(hook_name, "post-index-change"))
+				return write_post_index_change_sentinel(r);
+			if (!strcmp(hook_name, "post-command") &&
+			    !post_index_change_sentinel_exists(r))
+				return 0;
+		}
+	}
+
+	hook_path = find_hook(r, hook_name);
+
 	/*
 	 * Backwards compatibility hack in VFS for Git: when originally
 	 * introduced (and used!), it was called `post-indexchanged`, but this
@@ -252,12 +320,15 @@ int run_hooks_l(struct repository *r, const char *hook_name, ...)
 {
 	struct run_hooks_opt opt = RUN_HOOKS_OPT_INIT;
 	va_list ap;
+	int result;
 	const char *arg;
 
 	va_start(ap, hook_name);
 	while ((arg = va_arg(ap, const char *)))
 		strvec_push(&opt.args, arg);
 	va_end(ap);
 
-	return run_hooks_opt(r, hook_name, &opt);
+	result = run_hooks_opt(r, hook_name, &opt);
+	strvec_clear(&opt.args);
+	return result;
 }

t/t0401-post-command-hook.sh

@@ -22,6 +22,7 @@ test_expect_success 'with succeeding hook' '
 '
 
 test_expect_success 'with failing pre-command hook' '
+	test_when_finished rm -f .git/hooks/pre-command &&
 	write_script .git/hooks/pre-command <<-EOF &&
 	exit 1
 	EOF
@@ -30,4 +31,45 @@ test_expect_success 'with failing pre-command hook' '
 	test_path_is_missing "$(cat .git/post-command.out)"
 '
 
+test_expect_success 'with post-index-change config' '
+	mkdir -p .git/hooks &&
+	write_script .git/hooks/post-command <<-EOF &&
+	echo ran >post-command.out
+	EOF
+	write_script .git/hooks/post-index-change <<-EOF &&
+	echo ran >post-index-change.out
+	EOF
+
+	# First, show expected behavior.
+	echo ran >expect &&
+	rm -f post-command.out post-index-change.out &&
+
+	# rev-parse leaves index intact, but runs post-command.
+	git rev-parse HEAD &&
+	test_path_is_missing post-index-change.out &&
+	test_cmp expect post-command.out &&
+	rm -f post-command.out &&
+
+	echo stuff >>file &&
+	# add updates the index and runs post-command.
+	git add file &&
+	test_cmp expect post-index-change.out &&
+	test_cmp expect post-command.out &&
+
+	# Now, show configured behavior
+	git config postCommand.strategy post-index-change &&
+	rm -f post-command.out post-index-change.out &&
+
+	# rev-parse leaves index intact and thus skips post-command.
+	git rev-parse HEAD &&
+	test_path_is_missing post-index-change.out &&
+	test_path_is_missing post-command.out &&
+
+	echo stuff >>file &&
+	# add updates the index and runs post-command.
+	git add file &&
+	test_path_is_missing post-index-change.out &&
+	test_cmp expect post-command.out
+'
+
 test_done