chainsaw-update: log actual locks breaking

Previously, the command would simply state that it was about
to break locks, not if there was actually some to break.

This version is race-free. It would be also possible to display
the content of the lock before hand (not race-free but informative
in almost all cases).

hgext/chainsaw.py

@@ -120,9 +120,10 b' def update(ui, repo, **opts):'
         raise error.InputError(_(b'specify a target revision with --rev'))
     if not source:
         raise error.InputError(_(b'specify a pull path with --source'))
-    ui.status(_(b'breaking locks, if any\n'))
-    repo.svfs.tryunlink(b'lock')
-    repo.vfs.tryunlink(b'wlock')
+    if repo.svfs.tryunlink(b'lock'):
+        ui.status(_(b'had to break store lock\n'))
+    if repo.vfs.tryunlink(b'wlock'):
+        ui.status(_(b'had to break working copy lock\n'))
 
     ui.status(_(b'recovering after interrupted transaction, if any\n'))
     repo.recover()

tests/test-chainsaw-update.t

@@ -26,7 +26,6 b' Simple invocation'
   $ hg init repo
   $ cd repo
   $ hg admin::chainsaw-update --rev default --source ../src
-  breaking locks, if any
   recovering after interrupted transaction, if any
   no interrupted transaction available
   pulling from ../src
@@ -51,8 +50,15 b' from the current hostname (happens a lot'
   wlock: (.*?), process 171814, host invalid.host.test/effffffc \((\d+)s\) (re)
   [2]
 
-  $ hg admin::chainsaw-update --no-purge-ignored --rev default --source ../src -q
+  $ hg admin::chainsaw-update --no-purge-ignored --rev default --source ../src
+  had to break store lock
+  had to break working copy lock
+  recovering after interrupted transaction, if any
   no interrupted transaction available
+  pulling from ../src
+  updating to revision 'default'
+  0 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  chainsaw-update to revision 'default' for repository at '$TESTTMP/repo' done
 
 Test file purging capabilities
 ------------------------------