Re: [PATCH 2/3] name-rev: strip trailing ^0 in when --name-only

Ramkumar Ramachandra [off-list ref] writes:

236157 (Teach git-describe how to run name-rev, 2007-05-21) introduced
`git name-rev --name-only`, with the intent of using it to implement
`git describe --contains`.  According to the message, one of the primary
objectives of --name-only was to make the output of name-rev match that
of describe.

  $ git describe --contains --all master
  master

  $ git describe --contains --all master~1
  master~1

  $ git describe --contains --all v1.8.3~1
  v1.8.3~1

  $ git describe --contains --all v1.8.3
  v1.8.3^0

WRT "describe --contains", I do agree that both of these

    $ git describe $(git rev-parse v1.8.3^0)
    $ git describe --contains $(git rev-parse v1.8.3^0)
        
should just say "v1.8.3" without ~0/^0/~0~0~0 etc. and the last
example you showed will be improved by dropping ^0 at the end.

However.

I was a bit bothered by the description talking _only_ about
describe, but the actual change is to modify what name-rev gives its
direct users as well.  And that made me realize that the patch
itself has an undesirable side effect.

"describe" is _only_ about commit history graph, so in its context
v1.8.3 means the same thing as v1.8.3^0 (we never want to get a tag;
we always want a commit).  But I do not think "name-rev" is limited
to commits, in the sense that you would see this:

    $ git rev-parse v1.8.3 v1.8.3^0 | git name-rev --stdin
    8af06057d0c31a24e8737ae846ac2e116e8bafb9
    edca4152560522a431a51fc0a06147fc680b5b18 (tags/v1.8.3^0)

The second object is _not_ v1.8.3 but is v1.8.3^0 in the context of
name-rev, whose purpose is to give you a string you can feed
"rev-parse" and get the object name back.  "rev-parse v1.8.3" will
not give you the commit object name, so you need to keep "^0".

Junio C Hamano wrote:

But I do not think "name-rev" is limited
to commits, in the sense that you would see this:

    $ git rev-parse v1.8.3 v1.8.3^0 | git name-rev --stdin
    8af06057d0c31a24e8737ae846ac2e116e8bafb9
    edca4152560522a431a51fc0a06147fc680b5b18 (tags/v1.8.3^0)

The second object is _not_ v1.8.3 but is v1.8.3^0 in the context of
name-rev, whose purpose is to give you a string you can feed
"rev-parse" and get the object name back.  "rev-parse v1.8.3" will
not give you the commit object name, so you need to keep "^0".

Quite frankly, I thought the unstripped ^0 in one codepath was an
unintended quirk.  What exactly do you want name-rev to give you?

  $ git tag foo @^
  $ git name-rev foo
  foo tags/foo

So you can distinguish between annotated tags, unannotated tags, and
head-refs.  Can you get it to tell you anything reliably though?

  $ git tag bar @
  $ git tag -a baz @
  $ git name-rev @
  $ git name-rev bar
  $ git name-rev baz

ref, annotated, or unannotated tag?  I do not think name-rev is
fundamentally different from describe: it is also only dependent on
the commit history graph.  Whether I specify a revision using @, HEAD,
baz, or bar, I should get the same answer (it's just a recursive
peeler).  I'm not sure what you gain by knowing the object type of the
output.  If you wanted to feed something into rev-parse and get out a
commit, you'd send in $REV^0 without bothering about what it is, no?