• Ævar Arnfjörð Bjarmason's avatar
    get_short_oid: sort ambiguous objects by type, then SHA-1 · 5cc044e0
    Ævar Arnfjörð Bjarmason authored
    Change the output emitted when an ambiguous object is encountered so
    that we show tags first, then commits, followed by trees, and finally
    blobs. Within each type we show objects in hashcmp() order. Before
    this change the objects were only ordered by hashcmp().
    
    The reason for doing this is that the output looks better as a result,
    e.g. the v2.17.0 tag before this change on "git show e8f2" would
    display:
    
        hint: The candidates are:
        hint:   e8f2093055 tree
        hint:   e8f21caf commit 2013-06-24 - bash prompt: print unique detached HEAD abbreviated object name
        hint:   e8f21d02f7 blob
        hint:   e8f21d577c blob
        hint:   e8f25a3a50 tree
        hint:   e8f26250fa commit 2017-02-03 - Merge pull request #996 from jeffhostetler/jeffhostetler/register_rename_src
        hint:   e8f2650052 tag v2.17.0
        hint:   e8f2867228 blob
        hint:   e8f28d537c tree
        hint:   e8f2a35526 blob
        hint:   e8f2bc0c06 commit 2015-05-10 - Documentation: note behavior for multiple remote.url entries
        hint:   e8f2cf6ec0 tree
    
    Now we'll instead show:
    
        hint:   e8f2650052 tag v2.17.0
        hint:   e8f21caf commit 2013-06-24 - bash prompt: print unique detached HEAD abbreviated object name
        hint:   e8f26250fa commit 2017-02-03 - Merge pull request #996 from jeffhostetler/jeffhostetler/register_rename_src
        hint:   e8f2bc0c06 commit 2015-05-10 - Documentation: note behavior for multiple remote.url entries
        hint:   e8f2093055 tree
        hint:   e8f25a3a50 tree
        hint:   e8f28d537c tree
        hint:   e8f2cf6ec0 tree
        hint:   e8f21d02f7 blob
        hint:   e8f21d577c blob
        hint:   e8f2867228 blob
        hint:   e8f2a35526 blob
    
    Since we show the commit data in the output that's nicely aligned once
    we sort by object type. The decision to show tags before commits is
    pretty arbitrary. I don't want to order by object_type since there
    tags come last after blobs, which doesn't make sense if we want to
    show the most important things first.
    
    I could display them after commits, but it's much less likely that
    we'll display a tag, so if there is one it makes sense to show it
    prominently at the top.
    
    A note on the implementation: Derrick rightly pointed out[1] that
    we're bending over backwards here in get_short_oid() to first
    de-duplicate the list, and then emit it, but could simply do it in one
    step.
    
    The reason for that is that oid_array_for_each_unique() doesn't
    actually require that the array be sorted by oid_array_sort(), it just
    needs to be sorted in some order that guarantees that all objects with
    the same ID are adjacent to one another, which (barring a hash
    collision, which'll be someone else's problem) the sort_ambiguous()
    function does.
    
    I agree that would be simpler for this code, and had forgotten why I
    initially wrote it like this[2]. But on further reflection I think
    it's better to do more work here just so we're not underhandedly using
    the oid-array API where we lie about the list being sorted. That would
    break any subsequent use of oid_array_lookup() in subtle ways.
    
    I could get around that by hacking the API itself to support this
    use-case and documenting it, which I did as a WIP patch in [3], but I
    think it's too much code smell just for this one call site. It's
    simpler for the API to just introduce a oid_array_for_each() function
    to eagerly spew out the list without sorting or de-duplication, and
    then do the de-duplication and sorting in two passes.
    
    1. https://public-inbox.org/git/20180501130318.58251-1-dstolee@microsoft.com/
    2. https://public-inbox.org/git/876047ze9v.fsf@evledraar.gmail.com/
    3. https://public-inbox.org/git/874ljrzctc.fsf@evledraar.gmail.com/Helped-by: Derrick Stolee's avatarDerrick Stolee <dstolee@microsoft.com>
    Signed-off-by: Ævar Arnfjörð Bjarmason's avatarÆvar Arnfjörð Bjarmason <avarab@gmail.com>
    Signed-off-by: default avatarJunio C Hamano <gitster@pobox.com>
    5cc044e0
sha1-array.h 682 Bytes