[Request] [+ ] D8585: scmutil: speed up relativization of paths when it's a no-op

[valentin.gatienbaron (Valentin Gatien-Baron)]

valentin.gatienbaron created this revision.
Herald added a reviewer: hg-reviewers.
Herald added a subscriber: mercurial-patches.

REVISION SUMMARY
  Running commands from the root is commmon, in particular for
  automation. Running `hg files > /tmp/a` from the root of
  mozilla-central on linux:
  
  before:
  real	0m1,510s
  user	0m1,387s
  sys	0m0,090s
  
  after:
  real	0m1,266s
  user	0m1,165s
  sys	0m0,073s
  
  (there are 280k paths, so this was costing ~1us per path somehow)

REPOSITORY
  rHG Mercurial

BRANCH
  default

REVISION DETAIL
  https://phab.mercurial-scm.org/D8585

AFFECTED FILES
  mercurial/scmutil.py

CHANGE DETAILS

diff --git a/mercurial/scmutil.py b/mercurial/scmutil.py
--- a/mercurial/scmutil.py
+++ b/mercurial/scmutil.py
@@ -803,9 +803,12 @@
 
     if relative:
         cwd = repo.getcwd()
-        pathto = repo.pathto
-        return lambda f: pathto(f, cwd)
-    elif repo.ui.configbool(b'ui', b'slash'):
+        if cwd != b'':
+            # this branch is correct when cwd == b'', ie cwd = repo root,
+            # but it's slower
+            pathto = repo.pathto
+            return lambda f: pathto(f, cwd)
+    if repo.ui.configbool(b'ui', b'slash'):
         return lambda f: f
     else:
         return util.localpath



To: valentin.gatienbaron, #hg-reviewers
Cc: mercurial-patches, mercurial-devel
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