errors: introduce InputError and use it from commands and cmdutil This patch introduces a `InputError` class and replaces many uses of `error.Abort` by it in `commands` and `cmdutil`. This is a part of https://www.mercurial-scm.org/wiki/ErrorCategoriesPlan. There will later be a different class for state errors (to raise e.g. when there's an unfinished operation). It's not always clear when one should report an input error and when it should be a state error. We can always adjust later if I got something wrong in this patch (but feel free to point out any you notice now). Differential Revision: https://phab.mercurial-scm.org/D9167

--- a/mercurial/error.py	Wed Oct 21 19:00:16 2020 -0700
+++ b/mercurial/error.py	Tue Oct 06 22:36:15 2020 -0700
@@ -181,6 +181,13 @@
             return pycompat.sysstr(self.__bytes__())
 
 
+class InputError(Abort):
+    """Indicates that the user made an error in their input.
+
+    Examples: Invalid command, invalid flags, invalid revision.
+    """
+
+
 class HookLoadError(Abort):
     """raised when loading a hook fails, aborting an operation