On 2020-11-09 at 13:55:53, Johannes Schindelin wrote:
> Hi brian,
>
> On Fri, 9 Oct 2020, brian m. carlson wrote:
>
> > We'd like to canonicalize paths such that we can preserve any number of
> > trailing components that may be missing. Let's add a function to do
> > that that calls strbuf_realpath to find the canonical path for the
> > portion we do have and then append the missing part. We adjust
> > strip_last_component to return us the component it has stripped and use
> > that to help us accumulate the missing part.
> >
> > Note that it is intentional that we invoke strbuf_realpath here,
> > repeatedly if necessary, because on Windows that function is replaced
> > with a version that uses the proper system semantics for
> > canonicalization. Trying to adjust strbuf_realpath to perform this kind
> > of canonicalization with an additional option would fail to work
> > properly on Windows. The present approach is equivalent to
> > strbuf_realpath for cases where the path exists, and the only other
> > cases where we will use this function the additional overhead of
> > multiple invocations is not significant.
>
> Thank you for being so considerate. Yes, on Windows, we use (wherever
> possible) a shortcut that tells us the canonicalized path of existing
> entries.
>
> Technically, it is not `strbuf_realpath()` that we override, but we take a
> shortcut _in_ that function. That's semantics, though.
>
> More importantly, we recently fixed a bug in our code to allow for a quirk
> in the `strbuf_realpath()` function: `strbuf_realpath()` allows the last
> path component to not exist. If that is the case, now it's time to try
> without last component.
>
> In a sense, this is a 1-level version of your infinite-level
> `strbuf_realpath_missing()` function.
>
> An idea that immediately crosses my mind is whether that level could be
> something we want to pass directly into `strbuf_realpath()` as a parameter
> (it would be 1 to imitate the current behavior and -1 for the
> infinite-level case). What do you think? Does that make sense?
>
> In any case, I think this `_missing()` functionality should be implemented
> a bit more tightly with the `strbuf_realpath()` function because of the
> logic that already allows the last component to be missing:
>
> if (lstat(resolved->buf, &st)) {
> /* error out unless this was the last component */
> if (errno != ENOENT || remaining.len) {
> if (die_on_error)
> die_errno("Invalid path '%s'",
> resolved->buf);
> else
> goto error_out;
> }
>
> See https://github.com/git/git/blob/v2.29.2/abspath.c#L130-L138 for the
> exact code and context.
>
> Seeing as we _already_ have some code to allow for _some_ missing
> component, it should be possible to extend the logic to allow for
> different levels (e.g. using `count_slashes()` if we want to allow more
> than just the last component to be missing).
Okay, if you'd prefer to do it that way, that's fine with me. I'll
reroll with that change.
--
brian m. carlson (he/him or they/them)
Houston, Texas, US
Attachment:
signature.asc
Description: PGP signature
