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

From: Junio C Hamano <gitster@pobox.com>
Date: Mar 22, 2018, 17:01 UTC
Message-ID: <xmqq370sm4cv.fsf@gitster-ct.c.googlers.com>
In-Reply-To: <5ab3bd79.d14d650a.be5c0.8544@mx.google.com>

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

Show 9 quoted lines

>> 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.

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> 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.

Show 14 quoted lines

> 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).