tests/test-narrow-merge.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

#testcases flat tree

  $ . "$TESTDIR/narrow-library.sh"

#if tree
  $ cat << EOF >> $HGRCPATH
  > [experimental]
  > treemanifest = 1
  > EOF
#endif

create full repo

  $ hg init master
  $ cd master
  $ cat >> .hg/hgrc <<EOF
  > [narrow]
  > serveellipses=True
  > EOF

  $ mkdir inside
  $ echo inside1 > inside/f1
  $ echo inside2 > inside/f2
  $ mkdir outside
  $ echo outside1 > outside/f1
  $ echo outside2 > outside/f2
  $ hg ci -Aqm 'initial'

  $ echo modified > inside/f1
  $ hg ci -qm 'modify inside/f1'

  $ hg update -q 0
  $ echo modified > inside/f2
  $ hg ci -qm 'modify inside/f2'

  $ hg update -q 0
  $ echo modified2 > inside/f1
  $ hg ci -qm 'conflicting inside/f1'

  $ hg update -q 0
  $ echo modified > outside/f1
  $ hg ci -qm 'modify outside/f1'

  $ hg update -q 0
  $ echo modified2 > outside/f1
  $ hg ci -qm 'conflicting outside/f1'

  $ cd ..

  $ hg clone --narrow ssh://user@dummy/master narrow --include inside
  requesting all changes
  adding changesets
  adding manifests
  adding file changes
  added 6 changesets with 5 changes to 2 files (+4 heads)
  new changesets *:* (glob)
  updating to branch default
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ cd narrow

  $ hg update -q 0

Can merge in when no files outside narrow spec are involved

  $ hg update -q 'desc("modify inside/f1")'
  $ hg merge 'desc("modify inside/f2")'
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ hg commit -m 'merge inside changes'

Can merge conflicting changes inside narrow spec

  $ hg update -q 'desc("modify inside/f1")'
  $ hg merge 'desc("conflicting inside/f1")' 2>&1 | egrep -v '(warning:|incomplete!)'
  merging inside/f1
  0 files updated, 0 files merged, 0 files removed, 1 files unresolved
  use 'hg resolve' to retry unresolved file merges or 'hg merge --abort' to abandon
  $ echo modified3 > inside/f1
  $ hg resolve -m
  (no more unresolved files)
  $ hg commit -m 'merge inside/f1'

TODO: Can merge non-conflicting changes outside narrow spec

  $ hg update -q 'desc("modify inside/f1")'
  $ hg merge 'desc("modify outside/f1")'
  abort: merge affects file 'outside/f1' outside narrow, which is not yet supported (flat !)
  abort: merge affects file 'outside/' outside narrow, which is not yet supported (tree !)
  (merging in the other direction may work)
  [255]

  $ hg update -q 'desc("modify outside/f1")'
  $ hg merge 'desc("modify inside/f1")'
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ hg ci -m 'merge from inside to outside'

Refuses merge of conflicting outside changes

  $ hg update -q 'desc("modify outside/f1")'
  $ hg merge 'desc("conflicting outside/f1")'
  abort: conflict in file 'outside/f1' is outside narrow clone (flat !)
  abort: conflict in file 'outside/' is outside narrow clone (tree !)
  [255]