tests/test-rebase-bookmarks.t

cborutil: implement sans I/O decoder

The vendored CBOR package decodes by calling read(n) on an object.
There are a number of disadvantages to this:

* Uses blocking I/O. If sufficient data is not available, the decoder
  will hang until it is.
* No support for partial reads. If the read(n) returns less data than
  requested, the decoder raises an error.
* Requires the use of a file like object. If the original data is in
  say a buffer, we need to "cast" it to e.g. a BytesIO to appease the
  decoder.

In addition, the vendored CBOR decoder doesn't provide flexibility
that we desire. Specifically:

* It buffers indefinite length bytestrings instead of streaming them.
* It doesn't allow limiting the set of types that can be decoded. This
  property is useful when implementing a "hardened" decoder that is
  less susceptible to abusive input.
* It doesn't provide sufficient "hook points" and introspection to
  institute checks around behavior. These are useful for implementing
  a "hardened" decoder.

This all adds up to a reasonable set of justifications for writing our
own decoder.

So, this commit implements our own CBOR decoder.

At the heart of the decoder is a function that decodes a single "item"
from a buffer. This item can be a complete simple value or a special
value, such as "start of array." Using this function, we can build a
decoder that effectively iterates over the stream of decoded items and
builds up higher-level values, such as arrays, maps, sets, and indefinite
length bytestrings. And we can do this without performing I/O in the
decoder itself.

The core of the sans I/O decoder will probably not be used directly.
Instead, it is expected that we'll build utility functions for invoking
the decoder given specific input types. This will allow extreme
flexibility in how data is delivered to the decoder.

I'm pretty happy with the state of the decoder modulo the TODO items
to track wanted features to help with a "hardened" decoder. The one
thing I could be convinced to change is the handling of semantic tags.
Since we only support a single semantic tag (sets), I thought it would
be easier to handle them inline in decodeitem(). This is simpler now.
But if we add support for other semantic tags, it will likely be easier
to move semantic tag handling outside of decodeitem(). But, properly
supporting semantic tags opens up a whole can of worms, as many
semantic tags imply new types. I'm optimistic we won't need these in
Mercurial. But who knows.

I'm also pretty happy with the test coverage. Writing comprehensive
tests for partial decoding did flush out a handful of bugs. One
general improvement to testing would be fuzz testing for partial
decoding. I may implement that later. I also anticipate switching the
wire protocol code to this new decoder will flush out any lingering
bugs.

Differential Revision: https://phab.mercurial-scm.org/D4414

  $ cat >> $HGRCPATH <<EOF
  > [extensions]
  > rebase=
  > drawdag=$TESTDIR/drawdag.py
  > 
  > [phases]
  > publish=False
  > 
  > [alias]
  > tglog = log -G --template "{rev}: {node|short} '{desc}' bookmarks: {bookmarks}\n"
  > EOF

Create a repo with several bookmarks
  $ hg init a
  $ cd a

  $ echo a > a
  $ hg ci -Am A
  adding a

  $ echo b > b
  $ hg ci -Am B
  adding b
  $ hg book 'X'
  $ hg book 'Y'

  $ echo c > c
  $ hg ci -Am C
  adding c
  $ hg book 'Z'

  $ hg up -q 0

  $ echo d > d
  $ hg ci -Am D
  adding d
  created new head

  $ hg book W

  $ hg tglog
  @  3: 41acb9dca9eb 'D' bookmarks: W
  |
  | o  2: 49cb3485fa0c 'C' bookmarks: Y Z
  | |
  | o  1: 6c81ed0049f8 'B' bookmarks: X
  |/
  o  0: 1994f17a630e 'A' bookmarks:
  

Move only rebased bookmarks

  $ cd ..
  $ hg clone -q a a1

  $ cd a1
  $ hg up -q Z

Test deleting divergent bookmarks from dest (issue3685)

  $ hg book -r 3 Z@diverge

... and also test that bookmarks not on dest or not being moved aren't deleted

  $ hg book -r 3 X@diverge
  $ hg book -r 0 Y@diverge

  $ hg tglog
  o  3: 41acb9dca9eb 'D' bookmarks: W X@diverge Z@diverge
  |
  | @  2: 49cb3485fa0c 'C' bookmarks: Y Z
  | |
  | o  1: 6c81ed0049f8 'B' bookmarks: X
  |/
  o  0: 1994f17a630e 'A' bookmarks: Y@diverge
  
  $ hg rebase -s Y -d 3
  rebasing 2:49cb3485fa0c "C" (Y Z)
  saved backup bundle to $TESTTMP/a1/.hg/strip-backup/49cb3485fa0c-126f3e97-rebase.hg

  $ hg tglog
  @  3: 17fb3faba63c 'C' bookmarks: Y Z
  |
  o  2: 41acb9dca9eb 'D' bookmarks: W X@diverge
  |
  | o  1: 6c81ed0049f8 'B' bookmarks: X
  |/
  o  0: 1994f17a630e 'A' bookmarks: Y@diverge
  
Do not try to keep active but deleted divergent bookmark

  $ cd ..
  $ hg clone -q a a4

  $ cd a4
  $ hg up -q 2
  $ hg book W@diverge

  $ hg rebase -s W -d .
  rebasing 3:41acb9dca9eb "D" (W tip)
  saved backup bundle to $TESTTMP/a4/.hg/strip-backup/41acb9dca9eb-b35a6a63-rebase.hg

  $ hg bookmarks
     W                         3:0d3554f74897
     X                         1:6c81ed0049f8
     Y                         2:49cb3485fa0c
     Z                         2:49cb3485fa0c

Keep bookmarks to the correct rebased changeset

  $ cd ..
  $ hg clone -q a a2

  $ cd a2
  $ hg up -q Z

  $ hg rebase -s 1 -d 3
  rebasing 1:6c81ed0049f8 "B" (X)
  rebasing 2:49cb3485fa0c "C" (Y Z)
  saved backup bundle to $TESTTMP/a2/.hg/strip-backup/6c81ed0049f8-a687065f-rebase.hg

  $ hg tglog
  @  3: 3d5fa227f4b5 'C' bookmarks: Y Z
  |
  o  2: e926fccfa8ec 'B' bookmarks: X
  |
  o  1: 41acb9dca9eb 'D' bookmarks: W
  |
  o  0: 1994f17a630e 'A' bookmarks:
  

Keep active bookmark on the correct changeset

  $ cd ..
  $ hg clone -q a a3

  $ cd a3
  $ hg up -q X

  $ hg rebase -d W
  rebasing 1:6c81ed0049f8 "B" (X)
  rebasing 2:49cb3485fa0c "C" (Y Z)
  saved backup bundle to $TESTTMP/a3/.hg/strip-backup/6c81ed0049f8-a687065f-rebase.hg

  $ hg tglog
  o  3: 3d5fa227f4b5 'C' bookmarks: Y Z
  |
  @  2: e926fccfa8ec 'B' bookmarks: X
  |
  o  1: 41acb9dca9eb 'D' bookmarks: W
  |
  o  0: 1994f17a630e 'A' bookmarks:
  
  $ hg bookmarks
     W                         1:41acb9dca9eb
   * X                         2:e926fccfa8ec
     Y                         3:3d5fa227f4b5
     Z                         3:3d5fa227f4b5

rebase --continue with bookmarks present (issue3802)

  $ hg up 2
  0 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (leaving bookmark X)
  $ echo 'C' > c
  $ hg add c
  $ hg ci -m 'other C'
  created new head
  $ hg up 3
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg rebase --dest 4
  rebasing 3:3d5fa227f4b5 "C" (Y Z)
  merging c
  warning: conflicts while merging c! (edit, then use 'hg resolve --mark')
  unresolved conflicts (see hg resolve, then hg rebase --continue)
  [1]
  $ echo 'c' > c
  $ hg resolve --mark c
  (no more unresolved files)
  continue: hg rebase --continue
  $ hg rebase --continue
  rebasing 3:3d5fa227f4b5 "C" (Y Z)
  saved backup bundle to $TESTTMP/a3/.hg/strip-backup/3d5fa227f4b5-c6ea2371-rebase.hg
  $ hg tglog
  @  4: 45c0f0ec1203 'C' bookmarks: Y Z
  |
  o  3: b0e10b7175fd 'other C' bookmarks:
  |
  o  2: e926fccfa8ec 'B' bookmarks: X
  |
  o  1: 41acb9dca9eb 'D' bookmarks: W
  |
  o  0: 1994f17a630e 'A' bookmarks:
  

ensure that bookmarks given the names of revset functions can be used
as --rev arguments (issue3950)

  $ hg update -q 3
  $ echo bimble > bimble
  $ hg add bimble
  $ hg commit -q -m 'bisect'
  $ echo e >> bimble
  $ hg ci -m bisect2
  $ echo e >> bimble
  $ hg ci -m bisect3
  $ hg book bisect
  $ hg update -q Y
  $ hg rebase -r '"bisect"^^::"bisect"^' -r bisect -d Z
  rebasing 5:345c90f326a4 "bisect"
  rebasing 6:f677a2907404 "bisect2"
  rebasing 7:325c16001345 "bisect3" (bisect tip)
  saved backup bundle to $TESTTMP/a3/.hg/strip-backup/345c90f326a4-b4840586-rebase.hg

Bookmark and working parent get moved even if --keep is set (issue5682)

  $ hg init $TESTTMP/book-keep
  $ cd $TESTTMP/book-keep
  $ hg debugdrawdag <<'EOS'
  > B C
  > |/
  > A
  > EOS
  $ eval `hg tags -T 'hg bookmark -ir {node} {tag};\n' | grep -v tip`
  $ rm .hg/localtags
  $ hg up -q B
  $ hg tglog
  o  2: dc0947a82db8 'C' bookmarks: C
  |
  | @  1: 112478962961 'B' bookmarks: B
  |/
  o  0: 426bada5c675 'A' bookmarks: A
  
  $ hg rebase -r B -d C --keep
  rebasing 1:112478962961 "B" (B)
  $ hg tglog
  @  3: 9769fc65c4c5 'B' bookmarks: B
  |
  o  2: dc0947a82db8 'C' bookmarks: C
  |
  | o  1: 112478962961 'B' bookmarks:
  |/
  o  0: 426bada5c675 'A' bookmarks: A