[PATCH] {RFC} commands: switch to ctxmanager in phase

[Bryan O'Sullivan]

# HG changeset patch
# User Bryan O'Sullivan <bos at serpentine.com>
# Date 1452555256 28800
#      Mon Jan 11 15:34:16 2016 -0800
# Node ID e909e11e2d42cf419f2205e632f23a206a66d2f1
# Parent  03e3c89b14b24b99e63ec985e71d9ddd0ef7fcf1
{RFC} commands: switch to ctxmanager in phase

This is a small example of the kind of simplification that the ctxmanager class in the previous patch makes possible.

diff --git a/mercurial/commands.py b/mercurial/commands.py
--- a/mercurial/commands.py
+++ b/mercurial/commands.py
@@ -5438,7 +5438,6 @@ def phase(ui, repo, *revs, **opts):
 
     revs = scmutil.revrange(repo, revs)
 
-    lock = None
     ret = 0
     if targetphase is None:
         # display
@@ -5446,10 +5445,8 @@ def phase(ui, repo, *revs, **opts):
             ctx = repo[r]
             ui.write('%i: %s\n' % (ctx.rev(), ctx.phasestr()))
     else:
-        tr = None
-        lock = repo.lock()
-        try:
-            tr = repo.transaction("phase")
+        with util.ctxmanager(repo.lock, repo.translambda('phase')) as c:
+            tr = c()[1]
             # set phase
             if not revs:
                 raise error.Abort(_('empty revision set'))
@@ -5463,10 +5460,6 @@ def phase(ui, repo, *revs, **opts):
             if opts['force']:
                 phases.retractboundary(repo, tr, targetphase, nodes)
             tr.close()
-        finally:
-            if tr is not None:
-                tr.release()
-            lock.release()
         getphase = unfi._phasecache.phase
         newdata = [getphase(unfi, r) for r in unfi]
         changes = sum(newdata[r] != olddata[r] for r in unfi)