Re: [PATCH] filter-branch: consider refs can refer to an object other than commit or tag

[Junio C Hamano <gitster@pobox.com>]

Yuki Kokubun <orga.chem.job@gmail.com> writes:

>> Yuki Kokubun <orga.chem.job@gmail.com> writes:
>> 
>> >> Yuki Kokubun <orga.chem.job@gmail.com> writes:
>> >> 
>> >> > "git filter-branch -- --all" can be confused when refs that refer to objects
>> >> > other than commits or tags exists.
>> ...
>
> I meant the confusion is abnormal messages from the output of "git filter-branch -- --all".

OK, so it is not that the program logic gets confused and ends up
performing a wrong rewrite, but mostly that it gives confusing
messages.

> For example, this is an output of "git filter-branch -- --all":
>
> Rewrite bcdbd016c77df3d5641a3cf820b2ed46ba7bf3b4 (5/5) (0 seconds passed, remaining 0 predicted)
> WARNING: Ref 'refs/heads/master' is unchanged
> WARNING: Ref 'refs/heads/no-newline' is unchanged
> WARNING: Ref 'refs/heads/original' is unchanged

These are worth keeping, as I think existing users expect to see
them.

> error: object 1bf53b49c26465454e4ac377f2ed3f91bb1d6ac1 is a tree, not a commit
> error: object 1bf53b49c26465454e4ac377f2ed3f91bb1d6ac1 is a tree, not a commit
> fatal: ambiguous argument 'refs/replace/8a2016f3730cad8309c110f819c855403ed0a5b9^0': unknown revision or path not in the working tree.
> Use '--' to separate paths from revisions, like this:
> 'git <command> [<revision>...] -- [<file>...]'
> WARNING: Ref 'refs/replace/8a2016f3730cad8309c110f819c855403ed0a5b9' is unchanged
> WARNING: Ref 'refs/tags/add-file' is unchanged
> WARNING: Ref 'refs/tags/file' is unchanged
> error: object 1bf53b49c26465454e4ac377f2ed3f91bb1d6ac1 is a tree, not a commit
> error: object 1bf53b49c26465454e4ac377f2ed3f91bb1d6ac1 is a tree, not a commit
> fatal: ambiguous argument 'refs/tags/treetag^0': unknown revision or path not in the working tree.
> Use '--' to separate paths from revisions, like this:
> 'git <command> [<revision>...] -- [<file>...]'
> WARNING: Ref 'refs/tags/treetag' is unchanged

I think these warning messages should be kept, especially if we are
to keep the warning messages for the unchanged branches.  However,
the internal error messages are unwanted--these are implementation
details that reach the conclusion, i.e. the ref we were asked to
rewrite ended up being unchanged hence we did not touch it.

However, if we pre-filter to limit the refs in "$tempdir/heads" to
those that are committish (i.e. those that pass "$ref^0") like the
patch and subsequent discussion suggests, wouldn't we lose the
warning for these replace refs and non-committish tags.  We perhaps
could do something like:

	git rev-parse --no-flags ... >"$tempdir/raw-heads" || exit

	while read ref
	do
		case "$ref" in ^?*) continue ;; esac
		if git rev-parse --verify "$ref^0" 2>/dev/null
                then
			echo "$ref"
		else
			warn "WARNING: not rewriting '$ref' (not a committish)"
		fi
	done >"$tempdir/heads" <"$tempdir/raw-heads"

(note: the else clause is new, relative to my earlier suggestion).