Re: [PATCH v2 3/3] pretty: add abbrev option to %(describe)

> The %(describe) placeholder by default, like `git describe`, uses a
> seven-character abbreviated commit object name. This may not be
> sufficient to fully describe all commits in a given repository,
> resulting in a placeholder replacement changing its length because the
> repository grew in size.  This could cause the output of git-archive to
> change.
> 
> Add the --abbrev option to `git describe` to the placeholder interface
> in order to provide tools to the user for fine-tuning project defaults
> and ensure reproducible archives.
> 
> One alternative would be to just always specify --abbrev=40 but this may
> be a bit too biased...
> 
> Signed-off-by: Eli Schwartz <eschwartz@archlinux.org>
> ---
> 
> Notes:
>     With regard to validating that an integer is passed, I attempt to parse the
>     result using the same mechanism git-describe itself does in the abbrev
>     callback, just with slightly different validation of what we have at the end...
>     because of course here argval is the entire rest of the format string,
>     including the ")".
>     
>     While testing that this actually does what it's supposed to do, I noticed that
>     it doesn't validate junk like leading whitespace or plus signs... this is a
>     problem for `git describe --abbrev='    +15'` too so I guess it's not my
>     problem to fix...
> 
>  Documentation/pretty-formats.txt |  4 ++++
>  pretty.c                         | 16 +++++++++++++++-
>  t/t4205-log-pretty-formats.sh    |  8 ++++++++
>  3 files changed, 27 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/pretty-formats.txt b/Documentation/pretty-formats.txt
> index 86ed801aad..57fd84f579 100644
> --- a/Documentation/pretty-formats.txt
> +++ b/Documentation/pretty-formats.txt
> @@ -222,6 +222,10 @@ The placeholders are:
>  +
>  ** 'tags[=<BOOL>]': Instead of only considering annotated tags,
>     consider lightweight tags as well.
> +** 'abbrev=<N>': Instead of using the default number of hexadecimal digits
> +   (which will vary according to the number of objects in the repository with a
> +   default of 7) of the abbreviated object name, use <n> digits, or as many digits
> +   as needed to form a unique object name.
>  ** 'match=<pattern>': Only consider tags matching the given
>     `glob(7)` pattern, excluding the "refs/tags/" prefix.
>  ** 'exclude=<pattern>': Do not consider tags matching the given
> diff --git a/pretty.c b/pretty.c
> index 16b5366fed..44bfc49b38 100644
> --- a/pretty.c
> +++ b/pretty.c
> @@ -1218,9 +1218,10 @@ static size_t parse_describe_args(const char *start, struct strvec *args)
>  {
>  	struct {
>  		char *name;
> -		enum { OPT_BOOL, OPT_STRING, } type;
> +		enum { OPT_BOOL, OPT_INTEGER, OPT_STRING, } type;
>  	}  option[] = {
>  		{ "tags", OPT_BOOL},
> +		{ "abbrev", OPT_INTEGER },
>  		{ "exclude", OPT_STRING },
>  		{ "match", OPT_STRING },
>  	};
> @@ -1245,6 +1246,19 @@ static size_t parse_describe_args(const char *start, struct strvec *args)
>  					found = 1;
>  				}
>  				break;
> +			case OPT_INTEGER:
> +				if (match_placeholder_arg_value(arg, option[i].name, &arg,
> +								&argval, &arglen) && arglen) {
> +					if (!arglen)
> +						return 0;
> +					char* endptr;