tests/test-mq-symlinks.t

internals: document CBOR utilization

I spoke with some people at Mozilla about CBOR and they advised me
that we should be careful about the subset of CBOR we use in order
to mitigate security, performance, and compatibility concerns.

This commit establishes a document that attempts to formalize our
use of CBOR.

Its main limitations are on what types are allowed. It explicitly
enumerates which types are supported. Notable missing features
include:

* Indefinite-length arrays and maps
* Text strings (bytes all the way)
* Floats
* Date/time types
* Big integers
* Use of indefinite-length byte strings for map keys, values in
  containers.

If we have a need for any of these, we can have a discussion about
them when the time comes.

Differential Revision: https://phab.mercurial-scm.org/D4412

#require symlink

  $ echo "[extensions]" >> $HGRCPATH
  $ echo "mq=" >> $HGRCPATH

  $ hg init
  $ hg qinit
  $ hg qnew base.patch
  $ echo aaa > a
  $ echo bbb > b
  $ echo ccc > c
  $ hg add a b c
  $ hg qrefresh
  $ readlink.py a
  a -> a not a symlink


test replacing a file with a symlink

  $ hg qnew symlink.patch
  $ rm a
  $ ln -s b a
  $ hg qrefresh --git
  $ readlink.py a
  a -> b

  $ hg qpop
  popping symlink.patch
  now at: base.patch
  $ hg qpush
  applying symlink.patch
  now at: symlink.patch
  $ readlink.py a
  a -> b


test updating a symlink

  $ rm a
  $ ln -s c a
  $ hg qnew --git -f updatelink
  $ readlink.py a
  a -> c
  $ hg qpop
  popping updatelink
  now at: symlink.patch
  $ hg qpush --debug
  applying updatelink
  patching file a
  committing files:
  a
  committing manifest
  committing changelog
  updating the branch cache
  now at: updatelink
  $ readlink.py a
  a -> c
  $ hg st


test replacing a symlink with a file

  $ ln -s c s
  $ hg add s
  $ hg qnew --git -f addlink
  $ rm s
  $ echo sss > s
  $ hg qnew --git -f replacelinkwithfile
  $ hg qpop
  popping replacelinkwithfile
  now at: addlink
  $ hg qpush
  applying replacelinkwithfile
  now at: replacelinkwithfile
  $ cat s
  sss
  $ hg st


test symlink removal

  $ hg qnew removesl.patch
  $ hg rm a
  $ hg qrefresh --git
  $ hg qpop
  popping removesl.patch
  now at: replacelinkwithfile
  $ hg qpush
  applying removesl.patch
  now at: removesl.patch
  $ hg st -c
  C b
  C c
  C s

replace broken symlink with another broken symlink

  $ ln -s linka linka
  $ hg add linka
  $ hg qnew link
  $ hg mv linka linkb
  $ rm linkb
  $ ln -s linkb linkb
  $ hg qnew movelink
  $ hg qpop
  popping movelink
  now at: link
  $ hg qpush
  applying movelink
  now at: movelink
  $ readlink.py linkb
  linkb -> linkb