Junio C Hamano <gitster@xxxxxxxxx> writes:
> The function is given "len" from the caller to specify the minimum length
> of the output the caller expects (i.e. even if 4 hexdigits is enough to
> identify the given commit in a small project, the caller can say it wants
> to see at least 7 hexdigits). The loop without your patch finds the
> shortest prefix whose length is at least that given length that uniquely
> identifies the given object (or the shortest prefix that doesn't identify
> any existing object if the given sha1 does not exist in the repository).
> And then ensures the returned value is longer by the guard as an extra
> safety measure, so that later when the project grows, the disambiguation
> we find today has a better chance to survive.
> ...
> What am I missing?
I think what may be desirable is to honor the caller-supplied "len" a bit
better. If an object is uniquely identifiable with only 4-hexdigit today,
and if the caller gives 7 as len and the guard is set to 3, we return 10
hexdigits with the current code. We should instead return 7 hexdigits in
such a case, as that is in line with the "use 3 extra to give the
disambiguation we find today a better chance to survive".
Perhaps that was what you wanted to do, but I don't think that is what
your code actually does.
>
>> sha1_name.c | 5 ++++-
>> 1 files changed, 4 insertions(+), 1 deletions(-)
>>
>> diff --git a/sha1_name.c b/sha1_name.c
>> index 709ff2e..6bb8942 100644
>> --- a/sha1_name.c
>> +++ b/sha1_name.c
>> @@ -197,6 +197,7 @@ const char *find_unique_abbrev(const unsigned char *sha1, int len)
>> {
>> int status, exists;
>> static char hex[41];
>> + int extra_len = unique_abbrev_extra_length;
>>
>> exists = has_sha1_file(sha1);
>> memcpy(hex, sha1_to_hex(sha1), 40);
>> @@ -208,12 +209,14 @@ const char *find_unique_abbrev(const unsigned char *sha1, int len)
>> if (exists
>> ? !status
>> : status == SHORT_NAME_NOT_FOUND) {
>> - int cut_at = len + unique_abbrev_extra_length;
>> + int cut_at = len + extra_len;
>> cut_at = (cut_at < 40) ? cut_at : 40;
>> hex[cut_at] = 0;
>> return hex;
>> }
>> len++;
>> + if (extra_len > 0)
>> + extra_len--;
>> }
>> return hex;
>> }
--
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