tests/test-commit-multiple.t

run-tests: collect aggregate code coverage

Before this patch, every Python process during a code coverage run was
writing coverage data to the same file. I'm not sure if the coverage
package even tries to obtain a lock on the file. But what I do know is
there was some last write wins leading to loss of code coverage data, at
least with -j > 1.

This patch changes the code coverage mechanism to be multiple process
safe. The mechanism for initializing code coverage via sitecustomize.py
has been tweaked so each Python process will produce a separate coverage
data file on disk. Unless two processes generate the same random value,
there are no race conditions writing to the same file. At the end of the
test run, we combine all written files into an aggregate report.

On my machine, running the full test suite produces a little over
20,000 coverage files consuming ~350 MB. As you can imagine, it takes
several seconds to load and merge these coverage files. But when it is
done, you have an accurate picture of the aggregate code coverage for the
entire test suite, which is ~60% line coverage.

# reproduce issue2264, issue2516

create test repo
  $ cat <<EOF >> $HGRCPATH
  > [extensions]
  > transplant =
  > EOF
  $ hg init repo
  $ cd repo
  $ template="{rev}  {desc|firstline}  [{branch}]\n"

# we need to start out with two changesets on the default branch
# in order to avoid the cute little optimization where transplant
# pulls rather than transplants
add initial changesets
  $ echo feature1 > file1
  $ hg ci -Am"feature 1"
  adding file1
  $ echo feature2 >> file2
  $ hg ci -Am"feature 2"
  adding file2

# The changes to 'bugfix' are enough to show the bug: in fact, with only
# those changes, it's a very noisy crash ("RuntimeError: nothing
# committed after transplant").  But if we modify a second file in the
# transplanted changesets, the bug is much more subtle: transplant
# silently drops the second change to 'bugfix' on the floor, and we only
# see it when we run 'hg status' after transplanting.  Subtle data loss
# bugs are worse than crashes, so reproduce the subtle case here.
commit bug fixes on bug fix branch
  $ hg branch fixes
  marked working directory as branch fixes
  (branches are permanent and global, did you want a bookmark?)
  $ echo fix1 > bugfix
  $ echo fix1 >> file1
  $ hg ci -Am"fix 1"
  adding bugfix
  $ echo fix2 > bugfix
  $ echo fix2 >> file1
  $ hg ci -Am"fix 2"
  $ hg log -G --template="$template"
  @  3  fix 2  [fixes]
  |
  o  2  fix 1  [fixes]
  |
  o  1  feature 2  [default]
  |
  o  0  feature 1  [default]
  
transplant bug fixes onto release branch
  $ hg update 0
  1 files updated, 0 files merged, 2 files removed, 0 files unresolved
  $ hg branch release
  marked working directory as branch release
  (branches are permanent and global, did you want a bookmark?)
  $ hg transplant 2 3
  applying [0-9a-f]{12} (re)
  [0-9a-f]{12} transplanted to [0-9a-f]{12} (re)
  applying [0-9a-f]{12} (re)
  [0-9a-f]{12} transplanted to [0-9a-f]{12} (re)
  $ hg log -G --template="$template"
  @  5  fix 2  [release]
  |
  o  4  fix 1  [release]
  |
  | o  3  fix 2  [fixes]
  | |
  | o  2  fix 1  [fixes]
  | |
  | o  1  feature 2  [default]
  |/
  o  0  feature 1  [default]
  
  $ hg status
  $ hg status --rev 0:4
  M file1
  A bugfix
  $ hg status --rev 4:5
  M bugfix
  M file1

now test that we fixed the bug for all scripts/extensions
  $ cat > $TESTTMP/committwice.py <<__EOF__
  > from mercurial import ui, hg, match, node
  > from time import sleep
  > 
  > def replacebyte(fn, b):
  >     f = open(fn, "rb+")
  >     f.seek(0, 0)
  >     f.write(b)
  >     f.close()
  > 
  > def printfiles(repo, rev):
  >     print "revision %s files: %s" % (rev, repo[rev].files())
  > 
  > repo = hg.repository(ui.ui(), '.')
  > assert len(repo) == 6, \
  >        "initial: len(repo): %d, expected: 6" % len(repo)
  > 
  > replacebyte("bugfix", "u")
  > sleep(2)
  > try:
  >     print "PRE: len(repo): %d" % len(repo)
  >     wlock = repo.wlock()
  >     lock = repo.lock()
  >     replacebyte("file1", "x")
  >     repo.commit(text="x", user="test", date=(0, 0))
  >     replacebyte("file1", "y")
  >     repo.commit(text="y", user="test", date=(0, 0))
  >     print "POST: len(repo): %d" % len(repo)
  > finally:
  >     lock.release()
  >     wlock.release()
  > printfiles(repo, 6)
  > printfiles(repo, 7)
  > __EOF__
  $ $PYTHON $TESTTMP/committwice.py
  PRE: len(repo): 6
  POST: len(repo): 8
  revision 6 files: ['bugfix', 'file1']
  revision 7 files: ['file1']

Do a size-preserving modification outside of that process
  $ echo abcd > bugfix
  $ hg status
  M bugfix
  $ hg log --template "{rev}  {desc}  {files}\n" -r5:
  5  fix 2  bugfix file1
  6  x  bugfix file1
  7  y  file1

  $ cd ..