[PATCH 1 of 9 PoC] mq2: proof of concept for improving mq - starting point and tests

[Mads Kiilerich]

# HG changeset patch
# User Mads Kiilerich <madski at unity3d.com>
# Date 1409301979 -7200
#      Fri Aug 29 10:46:19 2014 +0200
# Node ID e426af93a42f11fb187793904b743b5b4341af6e
# Parent  926bc0d3b595caf37c5d70833a347eb43285de2f
mq2: proof of concept for improving mq - starting point and tests

These days it is trendy to bash mq and try to kill it. Instead, let's create
something better and let the winner win and let the loser go somewhere else and
die a quiet death.

Let's try to evolve and improve mq and give people the choice of using the tool
they prefer.

I kind of see mq as a tool for efficiently locally working on a number of
patches, while I more more see evolve as a tool modifying history under my
feet.

Problems/design goals to address:
 * Improve mq and try to remain backwards compatible.
 * Use merge and merge tools instead of patches and .rej files.
 * Better meta history without using tracked queues.
 * Consider evolve and the mindset that comes with it, be compatible or
   bridge the gab to it.

The basic ideas are:
 * Keep "stripped" (especially qpopped) changesets around instead of stripping
   them.
 * If possible, use these changesets for grafting when "qpushing".
 * Update patch files with reference to the last changeset it was qpushed as.
 * Get "rid" of qpopped changesets when they no longer are referenced -
   currently by using obsolete, could also strip them at that point.

Current issues:
 * Needs real testing.
 * Needs better error handling.
 * Better handling of the 'qpush failed with .rej files' scenario.
 ** It will now use merge - which is nice but requires test updates.
 ** How to represent that state (use nullid or a commit of something random?).
 ** How to continue from that state (qrefresh should pick it up).
 * Collision with already obsoleted changesets. Is that because obsolete markers
   are a bad solution to the problem ... or solving the wrong problem?
 * Some .unfiltered() has been added in various places. Is it just because
   this filtered hack is a *** hack or is there something wrong?

These changes are done incrementally in code, causing some test churn that mostly
ends up going away again. That is mostly because we start keeping "stripped"
changesets before we start hiding them.

diff --git a/tests/test-mq2.t b/tests/test-mq2.t
new file mode 100644
--- /dev/null
+++ b/tests/test-mq2.t
@@ -0,0 +1,153 @@
+  $ checkundo()
+  > {
+  >     if [ -f .hg/store/undo ]; then
+  >     echo ".hg/store/undo still exists after $1"
+  >     fi
+  > }
+
+  $ echo "[extensions]" >> $HGRCPATH
+  $ echo "mq=" >> $HGRCPATH
+
+  $ echo "[mq]" >> $HGRCPATH
+  $ echo "plain=false" >> $HGRCPATH
+
+  $ echo "[diff]" >> $HGRCPATH
+  $ echo "git=true" >> $HGRCPATH
+
+  $ hg init a
+  $ cd a
+  $ echo a > a
+  $ hg ci -Ama
+  adding a
+
+  $ hg qnew b -d '314159265 0'
+  $ echo b > b
+  $ hg add b
+  $ cat .hg/patches/b
+  # HG changeset patch
+  # Parent cb9a9f314b8b07ba71012fcdbc544b5a4d82ff5b
+  # Date 314159265 0
+  
+  $ hg qref -m b -d '47 0'
+  $ cat .hg/patches/b
+  # HG changeset patch
+  # Parent cb9a9f314b8b07ba71012fcdbc544b5a4d82ff5b
+  # Date 47 0
+  b
+  
+  diff --git a/b b/b
+  new file mode 100644
+  --- /dev/null
+  +++ b/b
+  @@ -0,0 +1,1 @@
+  +b
+
+  $ echo a2 >> a
+  $ hg qnew a2 -m a2 -d '117 0'
+
+  $ hg log -G --template "{rev} {node|short} {phase} {desc|firstline}\n"
+  @  2 757e6e08e7eb draft a2
+  |
+  o  1 3506c28d72aa draft b
+  |
+  o  0 cb9a9f314b8b draft a
+  
+
+  $ hg qpop
+  popping a2
+  now at: b
+
+  $ cat .hg/patches/status
+  3506c28d72aa3a31f8ce50ca4cfcb812af131450:b
+
+  $ hg log -G --template "{rev} {node|short} {phase} {desc|firstline}\n"
+  @  1 3506c28d72aa draft b
+  |
+  o  0 cb9a9f314b8b draft a
+  
+
+  $ hg qpush
+  applying a2
+  now at: a2
+
+  $ cat .hg/patches/status
+  3506c28d72aa3a31f8ce50ca4cfcb812af131450:b
+  757e6e08e7eb6b956e2d583ff4d7450d392f8a13:a2
+
+  $ hg log -G --template "{rev} {node|short} {phase} {desc|firstline}\n"
+  @  2 757e6e08e7eb draft a2
+  |
+  o  1 3506c28d72aa draft b
+  |
+  o  0 cb9a9f314b8b draft a
+  
+
+  $ hg qpop -a
+  popping a2
+  popping b
+  patch queue now empty
+  $ sed -i 1iyada a
+  $ hg ci -m yada
+
+  $ hg log -G --template "{rev} {node|short} {phase} {desc|firstline}\n"
+  @  1 dfa6dafa9c6c draft yada
+  |
+  o  0 cb9a9f314b8b draft a
+  
+
+  $ cat .hg/patches/b
+  # HG changeset patch
+  # Parent cb9a9f314b8b07ba71012fcdbc544b5a4d82ff5b
+  # Date 47 0
+  b
+  
+  diff --git a/b b/b
+  new file mode 100644
+  --- /dev/null
+  +++ b/b
+  @@ -0,0 +1,1 @@
+  +b
+  $ hg qpush
+  applying b
+  now at: b
+  $ cat .hg/patches/b
+  # HG changeset patch
+  # Parent cb9a9f314b8b07ba71012fcdbc544b5a4d82ff5b
+  # Date 47 0
+  b
+  
+  diff --git a/b b/b
+  new file mode 100644
+  --- /dev/null
+  +++ b/b
+  @@ -0,0 +1,1 @@
+  +b
+
+  $ hg qpush
+  applying a2
+  now at: a2
+  $ hg log -G --template "{rev} {node|short} {phase} {desc|firstline}\n"
+  @  3 cd192c2f0104 draft a2
+  |
+  o  2 c27d00b1f47f draft b
+  |
+  o  1 dfa6dafa9c6c draft yada
+  |
+  o  0 cb9a9f314b8b draft a
+  
+
+  $ hg qap
+  b
+  a2
+  $ hg qpop -a
+  popping a2
+  popping b
+  patch queue now empty
+  $ hg qrm b
+  $ hg qrm a2
+(should also have stripped b that couldn't be stripped before)
+  $ hg log -G --template "{rev} {node|short} {phase} {desc|firstline}\n"
+  @  1 dfa6dafa9c6c draft yada
+  |
+  o  0 cb9a9f314b8b draft a
+