[PATCH 3/3] hook-list.h: add a generated list of hooks, like config-list.h

["Ævar Arnfjörð Bjarmason" <avarab@gmail.com>]

Make githooks(5) the source of truth for what hooks git supports, and
die hooks we don't know about in find_hook(). This ensures that the
documentation and the C code's idea about existing hooks doesn't
diverge.

We still have Perl and Python code running its own hooks, but that'll
be addressed by Emily Shaffer's upcoming "git hook run" command.

This resolves a long-standing TODO item in bugreport.c of there being
no centralized listing of hooks, and fixes a bug with the bugreport
listing only knowing about 1/4 of the p4 hooks. It didn't know about
the recent "reference-transaction" hook either.

I have not been able to directly test the CMake change being made
here. Since 4c2c38e800 (ci: modification of main.yml to use cmake for
vs-build job, 2020-06-26) some of the Windows CI has a hard dependency
on CMake, this change works there, and is to my eyes an obviously
correct use of a pattern established in previous CMake changes,
namely:

 - 061c2240b1 (Introduce CMake support for configuring Git,
    2020-06-12)
 - 709df95b78 (help: move list_config_help to builtin/help,
    2020-04-16)
 - 976aaedca0 (msvc: add a Makefile target to pre-generate the Visual
   Studio solution, 2019-07-29)

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
---
 .gitignore                          |  1 +
 Makefile                            | 11 +++++++-
 builtin/bugreport.c                 | 44 ++++++-----------------------
 contrib/buildsystems/CMakeLists.txt |  7 +++++
 generate-hooklist.sh                | 24 ++++++++++++++++
 hook.c                              | 19 +++++++++++++
 6 files changed, 69 insertions(+), 37 deletions(-)
 create mode 100755 generate-hooklist.sh

diff --git a/.gitignore b/.gitignore
index 311841f9be..6be9de41ae 100644
--- a/.gitignore
+++ b/.gitignore
@@ -190,6 +190,7 @@
 /gitweb/static/gitweb.min.*
 /config-list.h
 /command-list.h
+/hook-list.h
 *.tar.gz
 *.dsc
 *.deb
diff --git a/Makefile b/Makefile
index d155b7be21..9bd31e1ac5 100644
--- a/Makefile
+++ b/Makefile
@@ -817,6 +817,8 @@ XDIFF_LIB = xdiff/lib.a
 
 GENERATED_H += command-list.h
 GENERATED_H += config-list.h
+GENERATED_H += hook-list.h
+
 .PHONY: generated-hdrs
 generated-hdrs: $(GENERATED_H)
 
@@ -2208,7 +2210,9 @@ git$X: git.o GIT-LDFLAGS $(BUILTIN_OBJS) $(GITLIBS)
 
 help.sp help.s help.o: command-list.h
 
-builtin/help.sp builtin/help.s builtin/help.o: config-list.h GIT-PREFIX
+hook.sp hook.s hook.o: hook-list.h
+
+builtin/help.sp builtin/help.s builtin/help.o: config-list.h hook-list.h GIT-PREFIX
 builtin/help.sp builtin/help.s builtin/help.o: EXTRA_CPPFLAGS = \
 	'-DGIT_HTML_PATH="$(htmldir_relative_SQ)"' \
 	'-DGIT_MAN_PATH="$(mandir_relative_SQ)"' \
@@ -2241,6 +2245,11 @@ command-list.h: $(wildcard Documentation/git*.txt)
 		$(patsubst %,--exclude-program %,$(EXCLUDED_PROGRAMS)) \
 		command-list.txt >$@+ && mv $@+ $@
 
+hook-list.h: generate-hooklist.sh
+hook-list.h: Documentation/githooks.txt
+	$(QUIET_GEN)$(SHELL_PATH) ./generate-hooklist.sh \
+		>$@+ && mv $@+ $@
+
 SCRIPT_DEFINES = $(SHELL_PATH_SQ):$(DIFF_SQ):$(GIT_VERSION):\
 	$(localedir_SQ):$(NO_CURL):$(USE_GETTEXT_SCHEME):$(SANE_TOOL_PATH_SQ):\
 	$(gitwebdir_SQ):$(PERL_PATH_SQ):$(SANE_TEXT_GREP):$(PAGER_ENV):\
diff --git a/builtin/bugreport.c b/builtin/bugreport.c
index 941c8d5e27..a7a1fcb8a7 100644
--- a/builtin/bugreport.c
+++ b/builtin/bugreport.c
@@ -4,6 +4,7 @@
 #include "help.h"
 #include "compat/compiler.h"
 #include "hook.h"
+#include "hook-list.h"
 
 
 static void get_system_info(struct strbuf *sys_info)
@@ -41,39 +42,7 @@ static void get_system_info(struct strbuf *sys_info)
 
 static void get_populated_hooks(struct strbuf *hook_info, int nongit)
 {
-	/*
-	 * NEEDSWORK: Doesn't look like there is a list of all possible hooks;
-	 * so below is a transcription of `git help hooks`. Later, this should
-	 * be replaced with some programmatically generated list (generated from
-	 * doc or else taken from some library which tells us about all the
-	 * hooks)
-	 */
-	static const char *hook[] = {
-		"applypatch-msg",
-		"pre-applypatch",
-		"post-applypatch",
-		"pre-commit",
-		"pre-merge-commit",
-		"prepare-commit-msg",
-		"commit-msg",
-		"post-commit",
-		"pre-rebase",
-		"post-checkout",
-		"post-merge",
-		"pre-push",
-		"pre-receive",
-		"update",
-		"post-receive",
-		"post-update",
-		"push-to-checkout",
-		"pre-auto-gc",
-		"post-rewrite",
-		"sendemail-validate",
-		"fsmonitor-watchman",
-		"p4-pre-submit",
-		"post-index-change",
-	};
-	int i;
+	const char **p;
 
 	if (nongit) {
 		strbuf_addstr(hook_info,
@@ -81,9 +50,12 @@ static void get_populated_hooks(struct strbuf *hook_info, int nongit)
 		return;
 	}
 
-	for (i = 0; i < ARRAY_SIZE(hook); i++)
-		if (hook_exists(hook[i]))
-			strbuf_addf(hook_info, "%s\n", hook[i]);
+	for (p = hook_name_list; *p; p++) {
+		const char *hook = *p;
+
+		if (hook_exists(hook))
+			strbuf_addf(hook_info, "%s\n", hook);
+	}
 }
 
 static const char * const bugreport_usage[] = {
diff --git a/contrib/buildsystems/CMakeLists.txt b/contrib/buildsystems/CMakeLists.txt
index a87841340e..c216940945 100644
--- a/contrib/buildsystems/CMakeLists.txt
+++ b/contrib/buildsystems/CMakeLists.txt
@@ -602,6 +602,13 @@ if(NOT EXISTS ${CMAKE_BINARY_DIR}/config-list.h)
 			OUTPUT_FILE ${CMAKE_BINARY_DIR}/config-list.h)
 endif()
 
+if(NOT EXISTS ${CMAKE_BINARY_DIR}/hook-list.h)
+	message("Generating hook-list.h")
+	execute_process(COMMAND ${SH_EXE} ${CMAKE_SOURCE_DIR}/generate-hooklist.sh
+			WORKING_DIRECTORY ${CMAKE_SOURCE_DIR}
+			OUTPUT_FILE ${CMAKE_BINARY_DIR}/hook-list.h)
+endif()
+
 include_directories(${CMAKE_BINARY_DIR})
 
 #build
diff --git a/generate-hooklist.sh b/generate-hooklist.sh
new file mode 100755
index 0000000000..5a3f7f849c
--- /dev/null
+++ b/generate-hooklist.sh
@@ -0,0 +1,24 @@
+#!/bin/sh
+
+echo "/* Automatically generated by generate-hooklist.sh */"
+
+print_hook_list () {
+	cat <<EOF
+static const char *hook_name_list[] = {
+EOF
+	perl -ne '
+		chomp;
+		@l[$.] = $_;
+		push @h => $l[$. - 1] if /^~~~+$/s;
+		END {
+			print qq[\t"$_",\n] for sort @h;
+		}
+	' <Documentation/githooks.txt
+	cat <<EOF
+	NULL,
+};
+EOF
+}
+
+echo
+print_hook_list
diff --git a/hook.c b/hook.c
index 97cd799a32..1f1db1ec9b 100644
--- a/hook.c
+++ b/hook.c
@@ -1,11 +1,30 @@
 #include "cache.h"
 #include "hook.h"
 #include "run-command.h"
+#include "hook-list.h"
+
+static int known_hook(const char *name)
+{
+	const char **p;
+	size_t len = strlen(name);
+	for (p = hook_name_list; *p; p++) {
+		const char *hook = *p;
+
+		if (!strncmp(name, hook, len) && hook[len] == '\0')
+			return 1;
+	}
+
+	return 0;
+}
 
 const char *find_hook(const char *name)
 {
 	static struct strbuf path = STRBUF_INIT;
 
+	if (!known_hook(name))
+		die(_("the hook '%s' is not known to git, should be in hook-list.h via githooks(5)"),
+		    name);
+
 	strbuf_reset(&path);
 	strbuf_git_path(&path, "hooks/%s", name);
 	if (access(path.buf, X_OK) < 0) {
-- 
2.32.0.576.g59759b6ca7d