view tests/test-rebase-pull.t @ 44950:f9734b2d59cc

py3: make stdout line-buffered if connected to a TTY

Status messages that are to be shown on the terminal should be written to the
file descriptor before anything further is done, to keep the user updated.

One common way to achieve this is to make stdout line-buffered if it is
connected to a TTY. This is done on Python 2 (except on Windows, where libc,
which the CPython 2 streams depend on, does not properly support this).

Python 3 rolls it own I/O streams. On Python 3, buffered binary streams can't be
set line-buffered. The previous code (added in 227ba1afcb65) incorrectly
assumed that on Python 3, pycompat.stdout (sys.stdout.buffer) is already
line-buffered. However the interpreter initializes it with a block-buffered
stream or an unbuffered stream (when the -u option or the PYTHONUNBUFFERED
environment variable is set), never with a line-buffered stream.

One example where the current behavior is unacceptable is when running
`hg pull https://www.mercurial-scm.org/repo/hg` on Python 3, where the line
"pulling from https://www.mercurial-scm.org/repo/hg" does not appear on the
terminal before the hg process blocks while waiting for the server.

Various approaches to fix this problem are possible, including:

1. Weaken the contract of procutil.stdout to not give any guarantees about
   buffering behavior. In this case, users of procutil.stdout need to be
   changed to do enough flushes. In particular,
  1. either ui must insert enough flushes for ui.write() and friends, or
  2. ui.write() and friends get split into flushing and fully buffered
     methods, or
  3. users of ui.write() and friends must flush explicitly.
2. Make stdout unbuffered.
3. Make stdout line-buffered. Since Python 3 does not natively support that for
   binary streams, we must implement it ourselves.

(2.) is problematic because using unbuffered I/O changes the performance
characteristics significantly compared to line-buffered (which is used on
Python 2) and this would be a regression.

(1.2.) and (1.3) are a substantial amount of work. It’s unclear whether the
added complexity would be justified, given that raw performance doesn’t matter
that much when writing to a terminal much faster than the user could read it.

(1.1.) pushes complexity into the ui class instead of separating the concern of
how stdout is buffered. Other users of procutil.stdout would still need to take
care of the flushes.

This patch implements (3.). The general performance considerations are very
similar to (1.1.). The extra method invocation and method forwarding add a
little more overhead if the class is used. In exchange, it doesn’t add overhead
if not used.


For the benchmarks, I compared the previous implementation (incorrect on Python
3), (1.1.), (3.) and (2.). The command was chosen so that the streams were
configured as if they were writing to a TTY, but actually write to a pager,
which is also the default:
HGRCPATH=/dev/null python3 ./hg --cwd ~/vcs/mozilla-central --time --pager yes --config pager.pager='cat > /dev/null' status --all

previous:
time: real 7.880 secs (user 7.290+0.050 sys 0.580+0.170)
time: real 7.830 secs (user 7.220+0.070 sys 0.590+0.140)
time: real 7.800 secs (user 7.210+0.050 sys 0.570+0.170)

(1.1.) using Yuya Nishihara’s patch:
time: real 9.860 secs (user 8.670+0.350 sys 1.160+0.830)
time: real 9.540 secs (user 8.430+0.370 sys 1.100+0.770)
time: real 9.830 secs (user 8.630+0.370 sys 1.180+0.840)

(3.) using this patch:
time: real 9.580 secs (user 8.480+0.350 sys 1.090+0.770)
time: real 9.670 secs (user 8.480+0.330 sys 1.170+0.860)
time: real 9.640 secs (user 8.500+0.350 sys 1.130+0.810)

(2.) using a previous patch by me:
time: real 10.480 secs (user 8.850+0.720 sys 1.590+1.500)
time: real 10.490 secs (user 8.750+0.750 sys 1.710+1.470)
time: real 10.240 secs (user 8.600+0.700 sys 1.590+1.510)


As expected, there’s no difference on Python 2, as exactly the same code paths
are used:

previous:
time: real 6.950 secs (user 5.870+0.330 sys 1.070+0.770)
time: real 7.040 secs (user 6.040+0.360 sys 0.980+0.750)
time: real 7.070 secs (user 5.950+0.360 sys 1.100+0.760)

this patch:
time: real 7.010 secs (user 5.900+0.390 sys 1.070+0.730)
time: real 7.000 secs (user 5.850+0.350 sys 1.120+0.760)
time: real 7.000 secs (user 5.790+0.380 sys 1.170+0.710)

  $ cat >> $HGRCPATH <<EOF
  > [extensions]
  > rebase=
  > histedit=
  > 
  > [alias]
  > tglog = log -G --template "{rev}: {node|short} '{desc}' {branches}\n"
  > EOF


  $ hg init a
  $ cd a

  $ echo C1 > C1
  $ hg ci -Am C1
  adding C1

  $ echo C2 > C2
  $ hg ci -Am C2
  adding C2

  $ cd ..

  $ hg clone a b
  updating to branch default
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved

  $ hg clone a c
  updating to branch default
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved

  $ cd b

  $ echo L1 > L1
  $ hg ci -Am L1
  adding L1


  $ cd ../a

  $ echo R1 > R1
  $ hg ci -Am R1
  adding R1


  $ cd ../b

Now b has one revision to be pulled from a:

  $ hg pull --rebase
  pulling from $TESTTMP/a
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 1 changes to 1 files (+1 heads)
  new changesets 77ae9631bcca
  rebasing 2:ff8d69a621f9 "L1"
  saved backup bundle to $TESTTMP/b/.hg/strip-backup/ff8d69a621f9-160fa373-rebase.hg

  $ hg tglog
  @  3: d80cc2da061e 'L1'
  |
  o  2: 77ae9631bcca 'R1'
  |
  o  1: 783333faa078 'C2'
  |
  o  0: 05d58a0c15dd 'C1'
  
Re-run:

  $ hg pull --rebase
  pulling from $TESTTMP/a
  searching for changes
  no changes found

Abort pull early if working dir is not clean:

  $ echo L1-mod > L1
  $ hg pull --rebase
  abort: uncommitted changes
  (cannot pull with rebase: please commit or shelve your changes first)
  [255]
  $ hg update --clean --quiet

Abort pull early if another operation (histedit) is in progress:

  $ hg histedit . -q --commands - << EOF
  > edit d80cc2da061e histedit: generate unfinished state
  > EOF
  Editing (d80cc2da061e), you may commit or record as needed now.
  (hg histedit --continue to resume)
  [1]
  $ hg pull --rebase
  abort: histedit in progress
  (use 'hg histedit --continue' or 'hg histedit --abort')
  [255]
  $ hg histedit --abort --quiet

Abort pull early with pending uncommitted merge:

  $ cd ..
  $ hg clone --noupdate c d
  $ cd d
  $ hg tglog
  o  1: 783333faa078 'C2'
  |
  o  0: 05d58a0c15dd 'C1'
  
  $ hg update --quiet 0
  $ echo M1 > M1
  $ hg commit --quiet -Am M1
  $ hg update --quiet 1
  $ hg merge 2
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ hg pull --rebase
  abort: outstanding uncommitted merge
  (cannot pull with rebase: please commit or shelve your changes first)
  [255]
  $ hg update --clean --quiet

Abort pull early with unclean subrepo:
  $ echo s = s > .hgsub
  $ hg add .hgsub
  $ hg init s
  $ hg commit -m "generated a subrepo"
  $ echo a > s/a
  $ hg -R s add s/a
  $ hg pull --rebase
  abort: uncommitted changes in subrepository "s"
  (cannot pull with rebase: please commit or shelve your changes first)
  [255]

Invoke pull --rebase and nothing to rebase:

  $ cd ../c

  $ hg book norebase
  $ hg pull --rebase
  pulling from $TESTTMP/a
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 1 changes to 1 files
  new changesets 77ae9631bcca
  nothing to rebase - updating instead
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  updating bookmark norebase

  $ hg tglog -l 1
  @  2: 77ae9631bcca 'R1'
  |
  ~

pull --rebase --update should ignore --update:

  $ hg pull --rebase --update
  pulling from $TESTTMP/a
  searching for changes
  no changes found

pull --rebase doesn't update if nothing has been pulled:

  $ hg up -q 1

  $ hg pull --rebase
  pulling from $TESTTMP/a
  searching for changes
  no changes found

  $ hg tglog -l 1
  o  2: 77ae9631bcca 'R1'
  |
  ~

  $ cd ..

pull --rebase works when a specific revision is pulled (issue3619)

  $ cd a
  $ hg tglog
  @  2: 77ae9631bcca 'R1'
  |
  o  1: 783333faa078 'C2'
  |
  o  0: 05d58a0c15dd 'C1'
  
  $ echo R2 > R2
  $ hg ci -Am R2
  adding R2
  $ echo R3 > R3
  $ hg ci -Am R3
  adding R3
  $ cd ../c
  $ hg tglog
  o  2: 77ae9631bcca 'R1'
  |
  @  1: 783333faa078 'C2'
  |
  o  0: 05d58a0c15dd 'C1'
  
  $ echo L1 > L1
  $ hg ci -Am L1
  adding L1
  created new head
  $ hg pull --rev tip --rebase
  pulling from $TESTTMP/a
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 2 changesets with 2 changes to 2 files
  new changesets 31cd3a05214e:770a61882ace
  rebasing 3:ff8d69a621f9 "L1"
  saved backup bundle to $TESTTMP/c/.hg/strip-backup/ff8d69a621f9-160fa373-rebase.hg
  $ hg tglog
  @  5: 518d153c0ba3 'L1'
  |
  o  4: 770a61882ace 'R3'
  |
  o  3: 31cd3a05214e 'R2'
  |
  o  2: 77ae9631bcca 'R1'
  |
  o  1: 783333faa078 'C2'
  |
  o  0: 05d58a0c15dd 'C1'
  
pull --rebase works with bundle2 turned on

  $ cd ../a
  $ echo R4 > R4
  $ hg ci -Am R4
  adding R4
  $ hg tglog
  @  5: 00e3b7781125 'R4'
  |
  o  4: 770a61882ace 'R3'
  |
  o  3: 31cd3a05214e 'R2'
  |
  o  2: 77ae9631bcca 'R1'
  |
  o  1: 783333faa078 'C2'
  |
  o  0: 05d58a0c15dd 'C1'
  
  $ cd ../c
  $ hg pull --rebase
  pulling from $TESTTMP/a
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 1 changes to 1 files (+1 heads)
  new changesets 00e3b7781125
  rebasing 5:518d153c0ba3 "L1"
  saved backup bundle to $TESTTMP/c/.hg/strip-backup/518d153c0ba3-73407f14-rebase.hg
  $ hg tglog
  @  6: 0d0727eb7ce0 'L1'
  |
  o  5: 00e3b7781125 'R4'
  |
  o  4: 770a61882ace 'R3'
  |
  o  3: 31cd3a05214e 'R2'
  |
  o  2: 77ae9631bcca 'R1'
  |
  o  1: 783333faa078 'C2'
  |
  o  0: 05d58a0c15dd 'C1'
  

pull --rebase only update if there is nothing to rebase

  $ cd ../a
  $ echo R5 > R5
  $ hg ci -Am R5
  adding R5
  $ hg tglog
  @  6: 88dd24261747 'R5'
  |
  o  5: 00e3b7781125 'R4'
  |
  o  4: 770a61882ace 'R3'
  |
  o  3: 31cd3a05214e 'R2'
  |
  o  2: 77ae9631bcca 'R1'
  |
  o  1: 783333faa078 'C2'
  |
  o  0: 05d58a0c15dd 'C1'
  
  $ cd ../c
  $ echo L2 > L2
  $ hg ci -Am L2
  adding L2
  $ hg up 'desc(L1)'
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ hg pull --rebase
  pulling from $TESTTMP/a
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 1 changes to 1 files (+1 heads)
  new changesets 88dd24261747
  rebasing 6:0d0727eb7ce0 "L1"
  rebasing 7:c1f58876e3bf "L2"
  saved backup bundle to $TESTTMP/c/.hg/strip-backup/0d0727eb7ce0-ef61ccb2-rebase.hg
  $ hg tglog
  o  8: 6dc0ea5dcf55 'L2'
  |
  @  7: 864e0a2d2614 'L1'
  |
  o  6: 88dd24261747 'R5'
  |
  o  5: 00e3b7781125 'R4'
  |
  o  4: 770a61882ace 'R3'
  |
  o  3: 31cd3a05214e 'R2'
  |
  o  2: 77ae9631bcca 'R1'
  |
  o  1: 783333faa078 'C2'
  |
  o  0: 05d58a0c15dd 'C1'
  

pull --rebase update (no rebase) use proper update:

- warn about other head.

  $ cd ../a
  $ echo R6 > R6
  $ hg ci -Am R6
  adding R6
  $ cd ../c
  $ hg up 'desc(R5)'
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ hg pull --rebase
  pulling from $TESTTMP/a
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 1 changes to 1 files (+1 heads)
  new changesets 65bc164c1d9b
  nothing to rebase - updating instead
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  updated to "65bc164c1d9b: R6"
  1 other heads for branch "default"
  $ hg tglog
  @  9: 65bc164c1d9b 'R6'
  |
  | o  8: 6dc0ea5dcf55 'L2'
  | |
  | o  7: 864e0a2d2614 'L1'
  |/
  o  6: 88dd24261747 'R5'
  |
  o  5: 00e3b7781125 'R4'
  |
  o  4: 770a61882ace 'R3'
  |
  o  3: 31cd3a05214e 'R2'
  |
  o  2: 77ae9631bcca 'R1'
  |
  o  1: 783333faa078 'C2'
  |
  o  0: 05d58a0c15dd 'C1'
  

Multiple pre-existing heads on the branch
-----------------------------------------

Pull bring content, but nothing on the current branch, we should not consider
pre-existing heads.

  $ cd ../a
  $ hg branch unrelatedbranch
  marked working directory as branch unrelatedbranch
  (branches are permanent and global, did you want a bookmark?)
  $ echo B1 > B1
  $ hg commit -Am B1
  adding B1
  $ cd ../c
  $ hg up 'desc(L2)'
  2 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ hg pull --rebase
  pulling from $TESTTMP/a
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 1 changes to 1 files
  new changesets 39c381359968
  nothing to rebase

There is two local heads and we pull a third one.
The second local head should not confuse the `hg pull rebase`.

  $ hg up 'desc(R6)'
  1 files updated, 0 files merged, 2 files removed, 0 files unresolved
  $ echo M1 > M1
  $ hg commit -Am M1
  adding M1
  $ cd ../a
  $ hg up 'desc(R6)'
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ echo R7 > R7
  $ hg commit -Am R7
  adding R7
  $ cd ../c
  $ hg up 'desc(L2)'
  2 files updated, 0 files merged, 2 files removed, 0 files unresolved
  $ hg pull --rebase
  pulling from $TESTTMP/a
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 1 changes to 1 files (+1 heads)
  new changesets f7d3e42052f9
  rebasing 7:864e0a2d2614 "L1"
  rebasing 8:6dc0ea5dcf55 "L2"
  saved backup bundle to $TESTTMP/c/.hg/strip-backup/864e0a2d2614-2f72c89c-rebase.hg
  $ hg tglog
  @  12: 3603a865eea0 'L2'
  |
  o  11: bcc8a9cd04bf 'L1'
  |
  o  10: f7d3e42052f9 'R7'
  |
  | o  9: 41fab4eef82f 'M1'
  |/
  | o  8: 39c381359968 'B1' unrelatedbranch
  |/
  o  7: 65bc164c1d9b 'R6'
  |
  o  6: 88dd24261747 'R5'
  |
  o  5: 00e3b7781125 'R4'
  |
  o  4: 770a61882ace 'R3'
  |
  o  3: 31cd3a05214e 'R2'
  |
  o  2: 77ae9631bcca 'R1'
  |
  o  1: 783333faa078 'C2'
  |
  o  0: 05d58a0c15dd 'C1'