Subject: Re: [PATCH] builtin/describe: introduce --broken flag

From: Junio C Hamano <[email-masked]>
Date: Tue, 21 Mar 2017 14:51:57 -0700

Stefan Beller <[email-masked]> writes:

> This patch helps to fix the root cause in [1], which tries to work around
> this situation.

I do not necessarily think it is reasonable to give $version-dirty
and proceed when a repository corruption is detected; if there is a
breakage in the repository, "git describe" is correct to die when a
populated submodule is broken.  IOW, I do not agree that [1] below
is working with a sensible expectation.

This is a tangent, but how does the Gerrit repository get corrupted
in the way described in [1] in the first place?  That might be what
needs to be corrected, perhaps?

>  Documentation/git-describe.txt |  7 +++++
>  builtin/describe.c             | 59 ++++++++++++++++++++++++++++++------------
>  t/t6120-describe.sh            | 20 ++++++++++++++
>  3 files changed, 70 insertions(+), 16 deletions(-)
>
> diff --git a/Documentation/git-describe.txt b/Documentation/git-describe.txt
> index 8755f3af7b..b71fa7a4ad 100644
> --- a/Documentation/git-describe.txt
> +++ b/Documentation/git-describe.txt
> @@ -34,6 +34,13 @@ OPTIONS
>  	It means describe HEAD and appends <mark> (`-dirty` by
>  	default) if the working tree is dirty.
>  
> +--broken[=<mark>]::
> +	Describe the working tree.
> +	It means describe HEAD and appends <mark> (`-broken` by
> +	default) if the working tree cannot be examined for dirtiness.
> +	This implies `--dirty`, which is the fallback behavior when
> +	the working tree examination works.

The wording for the "--dirty" is already awkward, but this one is
even more so ("Describe the working tree. It means" conveys no
useful information).  I however cannot come up with something much
better.  This is the best I could come up with:

	Describe the state of the working tree.  When the working
	tree matches HEAD, the output is the same as "git describe
	HEAD" and "-dirty" is appended to it if the working tree has
	local modification.  When a repository is corrupt and Git
	cannot determine if there is local modification, instead of
	dying, append "-broken" instead.

The last sentence can be tweaked to replace the description for
"--dirty".

> diff --git a/builtin/describe.c b/builtin/describe.c
> index 76c18059bf..37a83520c9 100644
> --- a/builtin/describe.c
> +++ b/builtin/describe.c
> @@ -9,6 +9,7 @@
>  #include "diff.h"
>  #include "hashmap.h"
>  #include "argv-array.h"
> +#include "run-command.h"
>  
>  #define SEEN		(1u << 0)
>  #define MAX_TAGS	(FLAG_BITS - 1)
> @@ -31,12 +32,7 @@ static int have_util;
>  static struct string_list patterns = STRING_LIST_INIT_NODUP;
>  static struct string_list exclude_patterns = STRING_LIST_INIT_NODUP;
>  static int always;
> -static const char *dirty;
> -
> -/* diff-index command arguments to check if working tree is dirty. */
> -static const char *diff_index_args[] = {
> -	"diff-index", "--quiet", "HEAD", "--", NULL
> -};
> +static const char *append, *dirty, *broken;

Perhaps call it "suffix" or something?

> +		if (broken) {
> +			struct child_process cp = CHILD_PROCESS_INIT;
> +			argv_array_pushl(&cp.args, "diff-index", "--quiet", "HEAD", "--", NULL);
> ...
> +			}
> +		} else if (dirty) {
> +			struct argv_array args = ARGV_ARRAY_INIT;
>  			static struct lock_file index_lock;
>  			int fd;
>  
> +			argv_array_pushl(&args, "diff-index", "--quiet", "HEAD", "--", NULL);

Somehow it looks like the patch is making the code a lot worse by
losing diff_index_args[] and duplicating the same command line twice
in the code.  Wouldn't argv_array_pushv() into these two different args
array from the same template work better?