tests/test-convert-cvs-branch.t

cborutil: change buffering strategy

Profiling revealed that we were spending a lot of time on the
line that was concatenating the old buffer with the incoming data
when attempting to decode long byte strings, such as manifest
revisions.

Essentially, we were feeding N chunks of size len(X) << len(Y) into
decode() and continuously allocating a new, larger buffer to hold
the undecoded input. This created substantial memory churn and
slowed down execution.

Changing the code to aggregate pending chunks in a list until we
have enough data to fully decode the next atom makes things much
more efficient.

I don't have exact data, but I recall the old code spending >1s
on manifest fulltexts from the mozilla-unified repo. The new code
doesn't significantly appear in profile output.

Differential Revision: https://phab.mercurial-scm.org/D4854

#require cvs

This is https://bz.mercurial-scm.org/1148
and https://bz.mercurial-scm.org/1447

  $ cvscall()
  > {
  >     cvs -f "$@" > /dev/null
  > }
  $ cat <<EOF >> $HGRCPATH
  > [extensions]
  > convert =
  > [convert]
  > cvsps.cache = 0
  > EOF

create cvs repository

  $ mkdir cvsrepo
  $ cd cvsrepo
  $ CVSROOT=`pwd`
  $ export CVSROOT
  $ CVS_OPTIONS=-f
  $ export CVS_OPTIONS
  $ cd ..
  $ rmdir cvsrepo
  $ cvscall -q -d "$CVSROOT" init

Create a new project

  $ mkdir src
  $ cd src
  $ echo "1" > a
  $ echo "1" > b
  $ cvscall import -m "init" src v0 r0 | sort
  $ cd ..
  $ cvscall co src
  cvs checkout: Updating src
  $ cd src

Branch the project

  $ cvscall tag -b BRANCH
  cvs tag: Tagging .
  $ cvscall up -r BRANCH > /dev/null
  cvs update: Updating .

Modify file a, then b, then a

  $ sleep 1
  $ echo "2" > a
  $ cvscall ci -m "mod a"
  cvs commit: Examining .
  $ echo "2" > b
  $ cvscall ci -m "mod b"
  cvs commit: Examining .
  $ sleep 1
  $ echo "3" > a
  $ cvscall ci -m "mod a again"
  cvs commit: Examining .

Convert

  $ cd ..
  $ hg convert src
  assuming destination src-hg
  initializing destination src-hg repository
  connecting to $TESTTMP/cvsrepo
  scanning source...
  collecting CVS rlog
  7 log entries
  creating changesets
  5 changeset entries
  sorting...
  converting...
  4 Initial revision
  3 init
  2 mod a
  1 mod b
  0 mod a again
  updating tags

Check the result

  $ hg -R src-hg log -G --template '{rev} ({branches}) {desc} files: {files}\n'
  o  5 () update tags files: .hgtags
  |
  | o  4 (BRANCH) mod a again files: a
  | |
  | o  3 (BRANCH) mod b files: b
  | |
  | o  2 (BRANCH) mod a files: a
  | |
  | o  1 (v0) init files:
  |/
  o  0 () Initial revision files: a b
  


issue 1447

  $ cvscall()
  > {
  >     cvs -f "$@" > /dev/null
  >     sleep 1
  > }
  $ cvsci()
  > {
  >     cvs -f ci "$@" >/dev/null
  >     sleep 1
  > }
  $ cvscall -Q -d `pwd`/cvsmaster2 init
  $ cd cvsmaster2
  $ CVSROOT=`pwd`
  $ export CVSROOT
  $ mkdir foo
  $ cd ..
  $ cvscall -Q co -d cvswork2 foo
  $ cd cvswork2
  $ echo foo > a.txt
  $ echo bar > b.txt
  $ cvscall -Q add a.txt b.txt
  $ cvsci -m "Initial commit"
  cvs commit: Examining .
  $ echo foo > b.txt
  $ cvsci -m "Fix b on HEAD"
  cvs commit: Examining .
  $ echo bar > a.txt
  $ cvsci -m "Small fix in a on HEAD"
  cvs commit: Examining .
  $ cvscall -Q tag -b BRANCH
  $ cvscall -Q up -P -rBRANCH
  $ echo baz > b.txt
  $ cvsci -m "Change on BRANCH in b"
  cvs commit: Examining .
  $ hg debugcvsps -x --parents foo
  collecting CVS rlog
  5 log entries
  creating changesets
  4 changeset entries
  ---------------------
  PatchSet 1 
  Date: * (glob)
  Author: * (glob)
  Branch: HEAD
  Tag: (none) 
  Log:
  Initial commit
  
  Members: 
  	a.txt:INITIAL->1.1 
  	b.txt:INITIAL->1.1 
  
  ---------------------
  PatchSet 2 
  Date: * (glob)
  Author: * (glob)
  Branch: HEAD
  Tag: (none) 
  Branchpoints: BRANCH 
  Parent: 1
  Log:
  Fix b on HEAD
  
  Members: 
  	b.txt:1.1->1.2 
  
  ---------------------
  PatchSet 3 
  Date: * (glob)
  Author: * (glob)
  Branch: HEAD
  Tag: (none) 
  Branchpoints: BRANCH 
  Parent: 2
  Log:
  Small fix in a on HEAD
  
  Members: 
  	a.txt:1.1->1.2 
  
  ---------------------
  PatchSet 4 
  Date: * (glob)
  Author: * (glob)
  Branch: BRANCH
  Tag: (none) 
  Parent: 3
  Log:
  Change on BRANCH in b
  
  Members: 
  	b.txt:1.2->1.2.2.1 
  

  $ cd ..