"dotless" local file paths do not work anymore since v0.5

[dzuelke]

Git allows relative paths in e.g. git clone, so the following all work:

dzuelke@localhost:~/Code/oss$ git clone git-url-parse-rs git-url-parse-rs-localclone
Cloning into 'git-url-parse-localclone'...
done.

dzuelke@localhost:~/Code/oss$ git clone ./git-url-parse-rs git-url-parse-rs-localclone
Cloning into 'git-url-parse-localclone'...
done.

dzuelke@localhost:~/Code/oss$ git clone ../oss/git-url-parse-rs git-url-parse-rs-localclone
Cloning into 'git-url-parse-localclone'...
done.

For file://, only absolute paths are allowed, and the host portion is ignored; this is all in compliance with RFC 8089:

dzuelke@localhost:~/Code/oss$ git clone git-url-parse-rs git-url-parse-rs-localclone
Cloning into 'git-url-parse-rs-localclone'...
fatal: no path specified; see 'git help pull' for valid url syntax

dzuelke@localhost:~/Code/oss$ git clone file://./git-url-parse-rs git-url-parse-rs-localclone
Cloning into 'git-url-parse-rs-localclone'...
fatal: '/git-url-parse-rs' does not appear to be a git repository
fatal: Could not read from remote repository.

Please make sure you have the correct access rights
and the repository exists.

dzuelke@localhost:~/Code/oss$ git clone file://$(pwd)/git-url-parse-rs git-url-parse-rs-localclone
Cloning into 'git-url-parse-rs-localclone'...
remote: Enumerating objects: 436, done.
remote: Counting objects: 100% (436/436), done.
remote: Compressing objects: 100% (226/226), done.
remote: Total 436 (delta 216), reused 364 (delta 180), pack-reused 0 (from 0)
Receiving objects: 100% (436/436), 119.95 KiB | 23.99 MiB/s, done.
Resolving deltas: 100% (216/216), done.

dzuelke@localhost:~/Code/oss$ git clone file://localhost$(pwd)/git-url-parse-rs git-url-parse-rs-localclone
Cloning into 'git-url-parse-rs-localclone'...
remote: Enumerating objects: 436, done.
remote: Counting objects: 100% (436/436), done.
remote: Compressing objects: 100% (226/226), done.
remote: Total 436 (delta 216), reused 364 (delta 180), pack-reused 0 (from 0)
Receiving objects: 100% (436/436), 119.95 KiB | 29.99 MiB/s, done.
Resolving deltas: 100% (216/216), done.

dzuelke@localhost:~/Code/oss$ git clone file://randomhost$(pwd)/git-url-parse-rs git-url-parse-rs-localclone
Cloning into 'git-url-parse-rs-localclone'...
remote: Enumerating objects: 436, done.
remote: Counting objects: 100% (436/436), done.
remote: Compressing objects: 100% (226/226), done.
remote: Total 436 (delta 216), reused 364 (delta 180), pack-reused 0 (from 0)
Receiving objects: 100% (436/436), 119.95 KiB | 29.99 MiB/s, done.
Resolving deltas: 100% (216/216), done.

This library currently supports the following:

• ./local/path (parses to ./local/path)
• ../local/path (parses to ../local/path)
• file://./local/path (parses to ./local/path, but according to RFC 8089 should be /local/path with a host of .)
• file://../local/path (parses to ../local/path, but according to RFC 8089 should be /local/path with a host of ..)

But not these:

• local/path (URL parse failed: InvalidPathEmpty)
• file://localhost/local/path (URL parse failed: InvalidFilePattern, but according to RFC 8089 should be /local/path with a host of localhost)
• file://anything/local/path (URL parse failed: InvalidFilePattern, but according to RFC 8089 should be /local/path with a host of anything)

These all worked in 0.4, although it normalized file://localhost/foo/bar to file:///foo/bar, but file://./foo/bar to file://./foo/bar (and the same for ..).

I think it would be useful to change the behavior to be compliant with RFC 8089 and with what Git supports, i.e., as follows:

• relative/path: allowed, yields relative/path;
• ./relative/path: allowed, yields ./relative/path;
• ../relative/path: allowed, yields ../relative/path;
• /absolute/path: allowed, yields /absolute/path;
• file://relative/path: allowed, yields /path (and a host of Some("relative"));
• file://./relative/path: allowed, yields /relative/path (and a host of Some("."));
• file://../relative/path: allowed, yields /relative/path (and a host of Some(".."));
• file:///absolute/path: allowed, yields /absolute/path (and a host of None)

This would also match the behavior of url::Url for file:// URLs.

The obvious trouble here is that url::Url cannot represent local-path URLs, so GitUrl::parse_to_url would fail for the relative path cases without a file:// scheme prefix, but IMO, that's acceptable as long as GitUrl::parse() supports it.