tests/test-origbackup-conflict.t

bundle2: implement consume() API on unbundlepart

We want bundle parts to not be seekable by default. That means
eliminating the generic seek() method.

A common pattern in bundle2.py is to seek to the end of the part
data. This is mainly used by the part iteration code to ensure
the underlying stream is advanced to the next bundle part.

In this commit, we establish a dedicated API for consuming a
bundle2 part data. We switch users of seek() to it.

The old implementation of seek(0, os.SEEK_END) would effectively
call self.read(). The new implementation calls self.read(32768)
in a loop. The old implementation would therefore assemble a
buffer to hold all remaining data being seeked over. For seeking
over large bundle parts, this would involve a large allocation and
a lot of overhead to collect intermediate data! This overhead can
be seen in the results for `hg perfbundleread`:

! bundle2 iterparts()
! wall 10.891305 comb 10.820000 user 7.990000 sys 2.830000 (best of 3)
! wall 8.070791 comb 8.060000 user 7.180000 sys 0.880000 (best of 3)
! bundle2 part seek()
! wall 12.991478 comb 10.390000 user 7.720000 sys 2.670000 (best of 3)
! wall 10.370142 comb 10.350000 user 7.430000 sys 2.920000 (best of 3)

Of course, skipping over large payload data isn't likely very common.
So I doubt the performance wins will be observed in the wild.

Differential Revision: https://phab.mercurial-scm.org/D1388

Set up repo

  $ cat << EOF >> $HGRCPATH
  > [ui]
  > origbackuppath=.hg/origbackups
  > [merge]
  > checkunknown=warn
  > EOF
  $ hg init repo
  $ cd repo
  $ echo base > base
  $ hg add base
  $ hg commit -m "base"

Make a dir named b that contains a file, and a file named d

  $ mkdir -p b
  $ echo c1 > b/c
  $ echo d1 > d
  $ hg add b/c d
  $ hg commit -m "c1"
  $ hg bookmark c1

Peform an update that causes b/c to be backed up

  $ hg up -q 0
  $ mkdir -p b
  $ echo c2 > b/c
  $ hg up --verbose c1
  resolving manifests
  b/c: replacing untracked file
  getting b/c
  creating directory: $TESTTMP/repo/.hg/origbackups/b (glob)
  getting d
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (activating bookmark c1)
  $ test -f .hg/origbackups/b/c

Make files named b and d

  $ hg up -q 0
  $ echo b1 > b
  $ echo d2 > d
  $ hg add b d
  $ hg commit -m b1
  created new head
  $ hg bookmark b1

Perform an update that causes b to be backed up - it should replace the backup b dir

  $ hg up -q 0
  $ echo b2 > b
  $ hg up --verbose b1
  resolving manifests
  b: replacing untracked file
  getting b
  removing conflicting directory: $TESTTMP/repo/.hg/origbackups/b (glob)
  getting d
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (activating bookmark b1)
  $ test -f .hg/origbackups/b

Perform an update the causes b/c to be backed up again - it should replace the backup b file

  $ hg up -q 0
  $ mkdir b
  $ echo c3 > b/c
  $ hg up --verbose c1
  resolving manifests
  b/c: replacing untracked file
  getting b/c
  creating directory: $TESTTMP/repo/.hg/origbackups/b (glob)
  removing conflicting file: $TESTTMP/repo/.hg/origbackups/b (glob)
  getting d
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (activating bookmark c1)
  $ test -d .hg/origbackups/b

Cause two symlinks to be backed up that points to a valid location from the backup dir

  $ hg up -q 0
  $ mkdir ../sym-link-target
#if symlink
  $ ln -s ../../../sym-link-target b
  $ ln -s ../../../sym-link-target d
#else
  $ touch b d
#endif
  $ hg up b1
  b: replacing untracked file
  d: replacing untracked file
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (activating bookmark b1)
#if symlink
  $ readlink.py .hg/origbackups/b
  .hg/origbackups/b -> ../../../sym-link-target
#endif

Perform an update that causes b/c and d to be backed up again - b/c should not go into the target dir

  $ hg up -q 0
  $ mkdir b
  $ echo c4 > b/c
  $ echo d3 > d
  $ hg up --verbose c1
  resolving manifests
  b/c: replacing untracked file
  d: replacing untracked file
  getting b/c
  creating directory: $TESTTMP/repo/.hg/origbackups/b (glob)
  removing conflicting file: $TESTTMP/repo/.hg/origbackups/b (glob)
  getting d
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (activating bookmark c1)
  $ cat .hg/origbackups/b/c
  c4
  $ cat .hg/origbackups/d
  d3
  $ ls ../sym-link-target

Incorrectly configure origbackuppath to be under a file

  $ echo data > .hg/badorigbackups
  $ hg up -q 0
  $ mkdir b
  $ echo c5 > b/c
  $ hg up --verbose c1 --config ui.origbackuppath=.hg/badorigbackups
  resolving manifests
  b/c: replacing untracked file
  getting b/c
  creating directory: $TESTTMP/repo/.hg/badorigbackups/b (glob)
  abort: The system cannot find the path specified: '$TESTTMP/repo/.hg/badorigbackups/b' (glob) (windows !)
  abort: Not a directory: '$TESTTMP/repo/.hg/badorigbackups/b' (no-windows !)
  [255]
  $ cat .hg/badorigbackups
  data