fix: allow tools to use :linerange, but also run if a file is unchanged The definition of "unchanged" here is subtle, because pure deletion diff hunks are ignored. That means this is different from using the --whole flag. This change allows you to configure, for example, a code formatter that: 1. Formats specific line ranges if specified via flags 2. Does not format the entire file when there are no line ranges provided 3. Performs some other kind of formatting regardless of provided line ranges This sounds a little far fetched, but it is meant to address a specific corner case encountered in Google's use of the fix extension. The default behavior is kept because it exists to prevent mistakes that could erase uncommitted changes. Differential Revision: https://phab.mercurial-scm.org/D6723