tests/test-rebase-emptycommit.t

bundle2: inline changegroup.readexactly()

Profiling reveals this loop is pretty tight. Literally any
function call elimination can make a big difference.

This commit inlines the relatively trivial changegroup.readexactly()
method inside the loop.

The results with `hg perfbundleread` on a bundle of the Firefox repo
speak for themselves:

! read(8k)
! wall 0.679730 comb 0.680000 user 0.140000 sys 0.540000 (best of 15)
! read(16k)
! wall 0.577228 comb 0.570000 user 0.080000 sys 0.490000 (best of 17)
! read(32k)
! wall 0.516060 comb 0.520000 user 0.040000 sys 0.480000 (best of 20)
! read(128k)
! wall 0.496378 comb 0.490000 user 0.010000 sys 0.480000 (best of 20)
! bundle2 iterparts()
! wall 3.460903 comb 3.460000 user 2.760000 sys 0.700000 (best of 3)
! wall 3.056811 comb 3.050000 user 2.340000 sys 0.710000 (best of 4)
! bundle2 iterparts() seekable
! wall 4.312722 comb 4.310000 user 3.480000 sys 0.830000 (best of 3)
! wall 4.007676 comb 4.000000 user 3.170000 sys 0.830000 (best of 3)
! bundle2 part seek()
! wall 6.754764 comb 6.740000 user 3.970000 sys 2.770000 (best of 3)
! wall 6.267110 comb 6.250000 user 3.480000 sys 2.770000 (best of 3)
! bundle2 part read(8k)
! wall 3.668004 comb 3.660000 user 2.960000 sys 0.700000 (best of 3)
! wall 3.404164 comb 3.400000 user 2.650000 sys 0.750000 (best of 3)
! bundle2 part read(16k)
! wall 3.489196 comb 3.480000 user 2.750000 sys 0.730000 (best of 3)
! wall 3.197972 comb 3.200000 user 2.490000 sys 0.710000 (best of 4)
! bundle2 part read(32k)
! wall 3.388569 comb 3.380000 user 2.640000 sys 0.740000 (best of 3)
! wall 3.060557 comb 3.060000 user 2.340000 sys 0.720000 (best of 4)
! bundle2 part read(128k)
! wall 3.276415 comb 3.270000 user 2.560000 sys 0.710000 (best of 4)
! wall 2.952209 comb 2.950000 user 2.230000 sys 0.720000 (best of 4)

Differential Revision: https://phab.mercurial-scm.org/D1392

  $ cat >> $HGRCPATH<<EOF
  > [extensions]
  > rebase=
  > drawdag=$TESTDIR/drawdag.py
  > EOF

  $ hg init non-merge
  $ cd non-merge
  $ hg debugdrawdag<<'EOS'
  >   F
  >   |
  >   E
  >   |
  >   D
  >   |
  > B C
  > |/
  > A
  > EOS

  $ for i in C D E F; do
  >   hg bookmark -r $i -i BOOK-$i
  > done

  $ hg debugdrawdag<<'EOS'
  > E
  > |
  > D
  > |
  > B
  > EOS

  $ hg log -G -T '{rev} {desc} {bookmarks}'
  o  7 E
  |
  o  6 D
  |
  | o  5 F BOOK-F
  | |
  | o  4 E BOOK-E
  | |
  | o  3 D BOOK-D
  | |
  | o  2 C BOOK-C
  | |
  o |  1 B
  |/
  o  0 A
  
With --keep, bookmark should move

  $ hg rebase -r 3+4 -d E --keep
  rebasing 3:e7b3f00ed42e "D" (BOOK-D)
  note: rebase of 3:e7b3f00ed42e created no changes to commit
  rebasing 4:69a34c08022a "E" (BOOK-E)
  note: rebase of 4:69a34c08022a created no changes to commit
  $ hg log -G -T '{rev} {desc} {bookmarks}'
  o  7 E BOOK-D BOOK-E
  |
  o  6 D
  |
  | o  5 F BOOK-F
  | |
  | o  4 E
  | |
  | o  3 D
  | |
  | o  2 C BOOK-C
  | |
  o |  1 B
  |/
  o  0 A
  
Move D and E back for the next test

  $ hg bookmark BOOK-D -fqir 3
  $ hg bookmark BOOK-E -fqir 4

Bookmark is usually an indication of a head. For changes that are introduced by
an ancestor of bookmark B, after moving B to B-NEW, the changes are ideally
still introduced by an ancestor of changeset on B-NEW. In the below case,
"BOOK-D", and "BOOK-E" include changes introduced by "C".

  $ hg rebase -s 2 -d E
  rebasing 2:dc0947a82db8 "C" (BOOK-C C)
  rebasing 3:e7b3f00ed42e "D" (BOOK-D)
  note: rebase of 3:e7b3f00ed42e created no changes to commit
  rebasing 4:69a34c08022a "E" (BOOK-E)
  note: rebase of 4:69a34c08022a created no changes to commit
  rebasing 5:6b2aeab91270 "F" (BOOK-F F)
  saved backup bundle to $TESTTMP/non-merge/.hg/strip-backup/dc0947a82db8-52bb4973-rebase.hg (glob)
  $ hg log -G -T '{rev} {desc} {bookmarks}'
  o  5 F BOOK-F
  |
  o  4 C BOOK-C BOOK-D BOOK-E
  |
  o  3 E
  |
  o  2 D
  |
  o  1 B
  |
  o  0 A
  
Merge and its ancestors all become empty

  $ hg init $TESTTMP/merge1
  $ cd $TESTTMP/merge1

  $ hg debugdrawdag<<'EOS'
  >     E
  >    /|
  > B C D
  >  \|/
  >   A
  > EOS

  $ for i in C D E; do
  >   hg bookmark -r $i -i BOOK-$i
  > done

  $ hg debugdrawdag<<'EOS'
  > H
  > |
  > D
  > |
  > C
  > |
  > B
  > EOS

  $ hg rebase -r '(A::)-(B::)-A' -d H
  rebasing 2:dc0947a82db8 "C" (BOOK-C)
  note: rebase of 2:dc0947a82db8 created no changes to commit
  rebasing 3:b18e25de2cf5 "D" (BOOK-D)
  note: rebase of 3:b18e25de2cf5 created no changes to commit
  rebasing 4:86a1f6686812 "E" (BOOK-E E)
  note: rebase of 4:86a1f6686812 created no changes to commit
  saved backup bundle to $TESTTMP/merge1/.hg/strip-backup/b18e25de2cf5-1fd0a4ba-rebase.hg (glob)

  $ hg log -G -T '{rev} {desc} {bookmarks}'
  o  4 H BOOK-C BOOK-D BOOK-E
  |
  o  3 D
  |
  o  2 C
  |
  o  1 B
  |
  o  0 A
  
Part of ancestors of a merge become empty

  $ hg init $TESTTMP/merge2
  $ cd $TESTTMP/merge2

  $ hg debugdrawdag<<'EOS'
  >     G
  >    /|
  >   E F
  >   | |
  > B C D
  >  \|/
  >   A
  > EOS

  $ for i in C D E F G; do
  >   hg bookmark -r $i -i BOOK-$i
  > done

  $ hg debugdrawdag<<'EOS'
  > H
  > |
  > F
  > |
  > C
  > |
  > B
  > EOS

  $ hg rebase -r '(A::)-(B::)-A' -d H
  rebasing 2:dc0947a82db8 "C" (BOOK-C)
  note: rebase of 2:dc0947a82db8 created no changes to commit
  rebasing 3:b18e25de2cf5 "D" (BOOK-D D)
  rebasing 4:03ca77807e91 "E" (BOOK-E E)
  rebasing 5:ad6717a6a58e "F" (BOOK-F)
  note: rebase of 5:ad6717a6a58e created no changes to commit
  rebasing 6:c58e8bdac1f4 "G" (BOOK-G G)
  saved backup bundle to $TESTTMP/merge2/.hg/strip-backup/b18e25de2cf5-2d487005-rebase.hg (glob)

  $ hg log -G -T '{rev} {desc} {bookmarks}'
  o    7 G BOOK-G
  |\
  | o  6 E BOOK-E
  | |
  o |  5 D BOOK-D BOOK-F
  |/
  o  4 H BOOK-C
  |
  o  3 F
  |
  o  2 C
  |
  o  1 B
  |
  o  0 A