Re: [PATCH 01/19] dir.c: optionally compute sha-1 of a .gitignore file

> Nguyễn Thái Ngọc Duy  <pclouds@gmail.com> writes:
>
>> This is not used anywhere yet. But the goal is to compare quickly if a
>> .gitignore file has changed when we have the SHA-1 of both old (cached
>> somewhere) and new (from index or a tree) versions.
>>
>> Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
>> ---
>>  dir.c | 50 +++++++++++++++++++++++++++++++++++++++++++-------
>>  dir.h |  5 +++++
>>  2 files changed, 48 insertions(+), 7 deletions(-)
>>
>> diff --git a/dir.c b/dir.c
>> index bd274a7..33a35c1 100644
>> --- a/dir.c
>> +++ b/dir.c
>> @@ -466,7 +466,8 @@ void add_exclude(const char *string, const char *base,
>>       x->el = el;
>>  }
>>
>> -static void *read_skip_worktree_file_from_index(const char *path, size_t *size)
>> +static void *read_skip_worktree_file_from_index(const char *path, size_t *size,
>> +                                             struct sha1_stat *ss)
>>  {
>>       int pos, len;
>>       unsigned long sz;
>> @@ -485,6 +486,10 @@ static void *read_skip_worktree_file_from_index(const char *path, size_t *size)
>>               return NULL;
>>       }
>>       *size = xsize_t(sz);
>> +     if (ss) {
>> +             memset(&ss->stat, 0, sizeof(ss->stat));
>> +             hashcpy(ss->sha1, active_cache[pos]->sha1);
>> +     }
>>       return data;
>>  }
>>
>> @@ -529,11 +534,18 @@ static void trim_trailing_spaces(char *buf)
>>               *last_space = '\0';
>>  }
>>
>> -int add_excludes_from_file_to_list(const char *fname,
>> -                                const char *base,
>> -                                int baselen,
>> -                                struct exclude_list *el,
>> -                                int check_index)
>> +/*
>> + * Given a file with name "fname", read it (either from disk, or from
>> + * the index if "check_index" is non-zero), parse it and store the
>> + * exclude rules in "el".
>> + *
>> + * If "ss" is not NULL, compute SHA-1 of the exclude file and fill
>> + * stat data from disk (only valid if add_excludes returns zero). If
>> + * ss_valid is non-zero, "ss" must contain good value as input.
>> + */
>
> Hmm, do we want a separate parameter for that?  Wouldn't it be
> sufficient and cleaner to pass is_null_sha1(ss->sha1[]),