Re: [PATCH v3] cherry-pick: make sure all input objects are commits

Thomas Rast [off-list ref] writes:

From a cursory glance it looks like it's actually an existing bug in
read_revisions_from_stdin or handle_revision_arg, depending on which way
you look at it.  read_revisions_from_stdin passes its temporary buffer
down to handle_revision_arg:

        struct strbuf sb;
        [...]
        strbuf_init(&sb, 1000);
        while (strbuf_getwholeline(&sb, stdin, '\n') != EOF) {
                [...]
                if (handle_revision_arg(sb.buf, revs, 0, REVARG_CANNOT_BE_FILENAME))
                        die("bad revision '%s'", sb.buf);
        }

But handle_revision_arg ends up just stuffing that parameter into the
revision-walker options via some helpers:

	add_rev_cmdline(revs, object, arg_, REV_CMD_REV, flags ^ local_flags);
	add_pending_object_with_mode(revs, object, arg, oc.mode);

This seems to have been lurking since 281eee4 (revision: keep track of
the end-user input from the command line, 2011-08-25).

Junio, at which level should we fix it?  We could of course have
read_revisions_from_stdin make a copy of the buffers it passes down, but
perhaps it would be less surprising to instead have handle_revision_arg
make sure it makes a copy of everything it "keeps"?

Looking at it again, it seems that the issue is much older than the
introduction of cmdline interface.

Everything we throw at add_pending_object() is assumed to be stable,
because historically they were argv[] strings, and --stdin is what
breaks that assumption.  Making copies unconditionally at the lower
layer only because some minority callers give it unstable strings
does not sound like a good trade-off.

So I changed my mind.  Your "easy fix" looks to me the right thing
to do.

The paths given to handle_refs() may also have to be copied before
saved, depending on how ref iteration is implemented, details of
which may change as Michael seems to be updating the area again.
I think we let the callback peek ref_entry->name[] which is stable,
so I suspect we are OK.