tests/test-dispatch.t

basectx: add an empty class that will be used as a parent of all contexts

At the moment, there is no simple way to check if an object is a context
because there is no common parent class. If there were, we could use
'isinstance' everywhere. Simply having memctx inherit from workingctx or
changectx would allow the use of 'isinstance' but that could lead to some
confusing situations of reading the code since we have three distinct concepts
of a context:

- changectx represents a changeset *already* in the repo, and is therefore immutable
- workingctx represents changes on disk in the working directory
- memctx represents changes solely in memory which may or may not be on disk

Therefore, I propose refactoring context.py to have all three contexts inherit
from a parent class 'basectx'.

test command parsing and dispatch

  $ hg init a
  $ cd a

Redundant options used to crash (issue436):
  $ hg -v log -v
  $ hg -v log -v x

  $ echo a > a
  $ hg ci -Ama
  adding a

Missing arg:

  $ hg cat
  hg cat: invalid arguments
  hg cat [OPTION]... FILE...
  
  output the current or given revision of files
  
  options:
  
   -o --output FORMAT       print output to file with formatted name
   -r --rev REV             print the given revision
      --decode              apply any matching decode filter
   -I --include PATTERN [+] include names matching the given patterns
   -X --exclude PATTERN [+] exclude names matching the given patterns
  
  [+] marked option can be specified multiple times
  
  use "hg help cat" to show the full help text
  [255]

[defaults]

  $ hg cat a
  a
  $ cat >> $HGRCPATH <<EOF
  > [defaults]
  > cat = -r null
  > EOF
  $ hg cat a
  a: no such file in rev 000000000000
  [1]

  $ cd "$TESTTMP"

OSError "No such file or directory" / "The system cannot find the path
specified" should include filename even when it is empty

  $ hg -R a archive ''
  abort: *: '' (glob)
  [255]

#if no-outer-repo

No repo:

  $ hg cat
  abort: no repository found in '$TESTTMP' (.hg not found)!
  [255]

#endif