template: add revset() template function
Adds a template function that executes a revset and returns the list of
revisions as the result. It has the signature 'revset(query [, args...])'. The
args are optional and are applied to the query string using the standard
python string.format(args) pattern. This allows things like:
'{revset("parents({0})", rev)}' to produce the parents of each individual
commit in the log output. If no args are specified, the revset result is
cached for the duration of the templater; so it's better to not use args if
performance is a concern.
By itself, revset() can be used to print commit parents, print the common
ancestor of a commit with the main branch, etc.
It can be used with the ifcontains() function to do things like
'{ifcontains(rev, revset('.'), label(...), ...)}' to color the working copy
parent, to color certain branches, to color draft commits, etc.
$ hg init
$ echo 123 > a
$ hg add a
$ hg commit -m "first" a
$ mkdir sub
$ echo 321 > sub/b
$ hg add sub/b
$ hg commit -m "second" sub/b
$ cat sub/b
321
$ hg co 0
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ cat sub/b 2>/dev/null || echo "sub/b not present"
sub/b not present
$ test -d sub || echo "sub not present"
sub not present