[PATCH] update: fix edge-case with update.atomic-file and read-only files

Boris Feld boris.feld at octobus.net
Fri Jan 11 15:24:28 UTC 2019


# HG changeset patch
# User Boris Feld <boris.feld at octobus.net>
# Date 1547128621 -3600
#      Thu Jan 10 14:57:01 2019 +0100
# Node ID 9d5ed4b088da0ece901b80c0fa40177cc6eaf676
# Parent  963462786f6e028563bcedc9008622e0f3b59c86
# EXP-Topic atomic-update-read-only
# Available At https://bitbucket.org/octobus/mercurial-devel/
#              hg pull https://bitbucket.org/octobus/mercurial-devel/ -r 9d5ed4b088da
update: fix edge-case with update.atomic-file and read-only files

We used to create the tempfile with the original file mode. That means
creating a read-only tempfile when the original file is read-only, which crash
if we need to write on the tempfile.

The file in the working directory ends up being writable with and without the
atomic update config, so the behavior is the same.

diff --git a/mercurial/util.py b/mercurial/util.py
--- a/mercurial/util.py
+++ b/mercurial/util.py
@@ -48,6 +48,7 @@ from . import (
     policy,
     pycompat,
     urllibcompat,
+    util
 )
 from .utils import (
     procutil,
@@ -2205,6 +2206,14 @@ class atomictempfile(object):
         self.__name = name      # permanent name
         self._tempname = mktempcopy(name, emptyok=('w' in mode),
                                     createmode=createmode)
+
+        # If we are gonna write on the tempfile, we need to make sure we have
+        # the permission to do so
+        if 'w' in mode and os.path.isfile(name):
+            oldstat = filestat.frompath(name)
+            newstat = oldstat.stat.st_mode | stat.S_IWUSR
+            os.chmod(self._tempname, newstat)
+
         self._fp = posixfile(self._tempname, mode)
         self._checkambig = checkambig
 
diff --git a/tests/test-update-atomic.t b/tests/test-update-atomic.t
new file mode 100644
--- /dev/null
+++ b/tests/test-update-atomic.t
@@ -0,0 +1,124 @@
+Checking that experimental.atomic-file works.
+
+  $ hg init .
+  $ cat > .hg/showwrites.py <<EOF
+  > def uisetup(ui):
+  >   from mercurial import vfs
+  >   class newvfs(vfs.vfs):
+  >     def __call__(self, *args, **kwargs):
+  >       print('vfs open', args, sorted(list(kwargs.items())))
+  >       return super(newvfs, self).__call__(*args, **kwargs)
+  >   vfs.vfs = newvfs
+  > EOF
+  $ for v in a1 a2 b1 b2 c ro; do echo $v > $v; done
+  $ chmod +x b*
+  $ hg commit -Aqm _
+
+# We check that
+# - the changes are actually atomic
+# - that permissions are correct (all 4 cases of (executable before) * (executable after))
+# - that renames work, though they should be atomic anyway
+# - that it works when source files are read-only (but directories are read-write still)
+
+  $ for v in a1 a2 b1 b2 ro; do echo changed-$v > $v; done
+  $ chmod -x *1; chmod +x *2
+  $ hg rename c d
+  $ hg commit -qm _
+
+Check behavior without update.atomic-file
+
+  $ hg update -r 0 -q
+  $ hg update -r 1 --config extensions.showwrites=.hg/showwrites.py |& grep "a1'.*wb"
+  ('vfs open', ('a1', 'wb'), [('atomictemp', False), ('backgroundclose', True)])
+
+  $ find * -printf "%f:%p:%m\n"
+  a1:a1:644
+  a2:a2:755
+  b1:b1:644
+  b2:b2:755
+  d:d:644
+  ro:ro:644
+
+Add a second revision for the ro file so we can test update when the file is
+present or not
+
+  $ echo "ro" > ro
+
+  $ hg commit -qm _
+
+Check behavior without update.atomic-file first
+
+  $ hg update -C -r 0 -q
+
+  $ hg update -r 1
+  6 files updated, 0 files merged, 1 files removed, 0 files unresolved
+
+  $ find * -printf "%f:%p:%m\n"
+  a1:a1:644
+  a2:a2:755
+  b1:b1:644
+  b2:b2:755
+  d:d:644
+  ro:ro:644
+
+Manually reset the mode of the read-only file
+
+  $ chmod a-w ro
+
+  $ find ro -printf "%f:%p:%m\n"
+  ro:ro:444
+
+Now the file is present and read-only
+
+  $ hg up -r 2
+  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
+
+  $ find ro -printf "%f:%p:%m\n"
+  ro:ro:644
+
+# The file which was read-only is now writable in the default behavior
+
+Check behavior with update.atomic-files
+
+
+  $ cat >> .hg/hgrc <<EOF
+  > [experimental]
+  > update.atomic-file = true
+  > EOF
+
+  $ hg update -C -r 0 -q
+  $ hg update -r 1 --config extensions.showwrites=.hg/showwrites.py |& grep "a1'.*wb"
+  ('vfs open', ('a1', 'wb'), [('atomictemp', True), ('backgroundclose', True)])
+  $ hg st -A --rev 1
+  C a1
+  C a2
+  C b1
+  C b2
+  C d
+  C ro
+
+Check the file permission after update
+  $ find * -printf "%f:%p:%m\n"
+  a1:a1:644
+  a2:a2:755
+  b1:b1:644
+  b2:b2:755
+  d:d:644
+  ro:ro:644
+
+Manually reset the mode of the read-only file
+
+  $ chmod a-w ro
+
+  $ find ro -printf "%f:%p:%m\n"
+  ro:ro:444
+
+Now the file is present and read-only
+
+  $ hg update -r 2
+  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
+
+  $ find ro -printf "%f:%p:%m\n"
+  ro:ro:644
+
+# The behavior is the same as without atomic update


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