Re: [PATCH v4 4/7] Implement `scalar diagnose`

> From: Johannes Schindelin <johannes.schindelin@gmx.de>
>
> Over the course of Scalar's development, it became obvious that there is
> a need for a command that can gather all kinds of useful information
> that can help identify the most typical problems with large
> worktrees/repositories.
>
> The `diagnose` command is the culmination of this hard-won knowledge: it
> gathers the installed hooks, the config, a couple statistics describing
> the data shape, among other pieces of information, and then wraps
> everything up in a tidy, neat `.zip` archive.
>
> Note: originally, Scalar was implemented in C# using the .NET API, where
> we had the luxury of a comprehensive standard library that includes
> basic functionality such as writing a `.zip` file. In the C version, we
> lack such a commodity. Rather than introducing a dependency on, say,
> libzip, we slightly abuse Git's `archive` machinery: we write out a
> `.zip` of the empty try, augmented by a couple files that are added via
> the `--add-file*` options. We are careful trying not to modify the
> current repository in any way lest the very circumstances that required
> `scalar diagnose` to be run are changed by the `diagnose` run itself.
>
> Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
> ---
>  contrib/scalar/scalar.c          | 144 +++++++++++++++++++++++++++++++
>  contrib/scalar/scalar.txt        |  12 +++
>  contrib/scalar/t/t9099-scalar.sh |  14 +++
>  3 files changed, 170 insertions(+)
>
> diff --git a/contrib/scalar/scalar.c b/contrib/scalar/scalar.c
> index 00dcd4b50ef..367a2c50e25 100644
> --- a/contrib/scalar/scalar.c
> +++ b/contrib/scalar/scalar.c
> @@ -11,6 +11,7 @@
>  #include "dir.h"
>  #include "packfile.h"
>  #include "help.h"
> +#include "archive.h"
>  
>  /*
>   * Remove the deepest subdirectory in the provided path string. Path must not
> @@ -261,6 +262,47 @@ static int unregister_dir(void)
>  	return res;
>  }
>  
> +static int add_directory_to_archiver(struct strvec *archiver_args,
> +					  const char *path, int recurse)
> +{
> +	int at_root = !*path;
> +	DIR *dir = opendir(at_root ? "." : path);
> +	struct dirent *e;
> +	struct strbuf buf = STRBUF_INIT;
> +	size_t len;
> +	int res = 0;
> +
> +	if (!dir)
> +		return error(_("could not open directory '%s'"), path);