Re: [PATCH v3 5/9] bugreport: collect list of populated hooks

[Johannes Schindelin <Johannes.Schindelin@gmx.de>]

Hi Emily,

On Thu, 24 Oct 2019, Emily Shaffer wrote:

> Occasionally a failure a user is seeing may be related to a specific
> hook which is being run, perhaps without the user realizing. While the
> contents of hooks can be sensitive - containing user data or process
> information specific to the user's organization - simply knowing that a
> hook is being run at a certain stage can help us to understand whether
> something is going wrong.
>
> Without a definitive list of hook names within the code, we compile our
> own list from the documentation. This is likely prone to bitrot. To
> reduce the amount of code humans need to read, we turn the list into a
> string_list and iterate over it (as we are calling the same find_hook
> operation on each string). However, since bugreport should primarily be
> called by the user, the performance loss from massaging the string
> seems acceptable.

Good idea!

>
> Signed-off-by: Emily Shaffer <emilyshaffer@google.com>
> ---
>  bugreport.c         | 44 ++++++++++++++++++++++++++++++++++++++++++++
>  bugreport.h         |  6 ++++++
>  builtin/bugreport.c |  4 ++++
>  3 files changed, 54 insertions(+)
>
> diff --git a/bugreport.c b/bugreport.c
> index afa4836ab1..9d7f44ff28 100644
> --- a/bugreport.c
> +++ b/bugreport.c
> @@ -103,3 +103,47 @@ void get_whitelisted_config(struct strbuf *config_info)
>  	strbuf_reset(config_info);
>  	strbuf_addbuf(config_info, &configs_and_values);
>  }
> +
> +void get_populated_hooks(struct strbuf *hook_info)
> +{
> +	/*
> +	 * Doesn't look like there is a list of all possible hooks; so below is
> +	 * a transcription of `git help hook`.
> +	 */
> +	const char *hooks = "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-changex";

Well, this is disappointing: I tried to come up with a scripted way to
extract the commit names from our source code, and I failed! This is
where I gave up:

	git grep run_hook |
	sed -n 's/.*run_hook[^(]*([^,]*, *\([^,]*\).*/\1/p' |
	sed -e '/^name$/d' -e '/^const char \*name$/d' \
		-e 's/push_to_checkout_hook/"push-to-checkout"/' |
	sort |
	uniq

This prints only the following hook names:

	"applypatch-msg"
	"post-applypatch"
	"post-checkout"
	"post-index-change"
	"post-merge"
	"pre-applypatch"
	"pre-auto-gc"
	"pre-rebase"
	"prepare-commit-msg"
	"push-to-checkout"

But at least it was easy to script the extracting from the
Documentation:

	sed -n '/^[a-z]/{N;/\n~~~/{s/\n.*//;p}}' \
		Documentation/githooks.txt

> +	struct string_list hooks_list = STRING_LIST_INIT_DUP;
> +	struct string_list_item *iter = NULL;
> +
> +	strbuf_reset(hook_info);
> +
> +	string_list_split(&hooks_list, hooks, ',', -1);
> +
> +	for_each_string_list_item(iter, &hooks_list) {

This should definitely be done at compile time, I think. We should be
able to generate an appropriate header via something like this:

	cat >hook-names.h <<-EOF
	static const char *hook_names[] = {
	$(sed -n '/^[a-z]/{N;/\n~~~/{s/\n.*/",/;s/^/	"/;p}}' \
		Documentation/githooks.txt)
	};
	EOF

Then you would use a simple `for()` loop using `ARRAY_SIZE()` to
iterate over the hook names.

> +		if (find_hook(iter->string)) {
> +			strbuf_addstr(hook_info, iter->string);
> +			strbuf_complete_line(hook_info);
> +		}
> +	}
> +}
> diff --git a/bugreport.h b/bugreport.h
> index 7413e7e1be..942a5436e3 100644
> --- a/bugreport.h
> +++ b/bugreport.h
> @@ -12,3 +12,9 @@ void get_system_info(struct strbuf *sys_info);
>   * config_info will be discarded.
>   */
>  void get_whitelisted_config(struct strbuf *sys_info);
> +
> +/**
> + * Adds the paths to all configured hooks (but not their contents). The previous
> + * contents of hook_info will be discarded.
> + */
> +void get_populated_hooks(struct strbuf *hook_info);
> diff --git a/builtin/bugreport.c b/builtin/bugreport.c
> index 70fe0d2b85..a0eefba498 100644
> --- a/builtin/bugreport.c
> +++ b/builtin/bugreport.c
> @@ -60,6 +60,10 @@ int cmd_bugreport(int argc, const char **argv, const char *prefix)
>  	get_whitelisted_config(&buffer);
>  	strbuf_write(&buffer, report);
>
> +	add_header(report, "Populated Hooks");

Wait! I should have stumbled over this in an earlier patch. The
`add_header()` function should not take a `FILE *` parameter at all, but
instead an `struct strbuf *` one!

Ciao,
Dscho

> +	get_populated_hooks(&buffer);
> +	strbuf_write(&buffer, report);
> +
>  	fclose(report);
>
>  	launch_editor(report_path.buf, NULL, NULL);
> --
> 2.24.0.rc0.303.g954a862665-goog
>
>