Mercurial appears to resolve cwd-relative path first, so "glob:*.c" could be
parsed as "**/*.c" if cwd was literally "**". It wouldn't practically matter,
but isn't correct. Instead, jj's parser first splits glob into literal part
and pattern. That's mainly because we want to parse the user input texts into
type-safe objects, and (RepoPathBuf, glob::Pattern) pairs are the simplest
ones. The current parser can't handle patterns like "foo/*/.." (= "foo" ?),
and errors out. I believe this restriction is acceptable.
Unlike literal paths, the 'glob:' pattern anchors to the whole file path. I
don't think "prefix"-matching glob is useful, and making it the default would
be rather confusing.
If this doesn't work out, maybe we can try one of these:
a. fall back to bare file name if expression doesn't contain any operator-like
characters (e.g. "f(x" is an error, but "f x" can be parsed as bare string)
b. introduce command-line flag to opt in (e.g. -e FILESET)
c. introduce pattern prefix to opt in (e.g. set:FILESET)
Closes#3239, #2915, #2286
