purge: abort with missing files avoiding problems with name-mangling fs

In a name mangling filesystem (e.g. a case insensitive one)
dirstate.walk() can yield filenames different from the ones
stored in the dirstate. This already confuses the status and
add commands, but with purge this may cause data loss.

To prevent this purge refuses to work if there are missing
files and has a 'force' option if the user knows it is safe.

Even with the force option purge checks if any of the missing
files is still available in the working dir: if so there
may be some problem with the underlying filesystem, so it
unconditionally aborts.

contrib/purge/purge.py

@@ -31,7 +31,8 b' from mercurial import hg, util'
 from mercurial.i18n import _
 import os
 
-def dopurge(ui, repo, dirs=None, act=True, abort_on_err=False, eol='\n'):
+def dopurge(ui, repo, dirs=None, act=True, abort_on_err=False, eol='\n',
+            force=False):
     def error(msg):
         if abort_on_err:
             raise util.Abort(msg)
@@ -49,14 +50,19 b' def dopurge(ui, repo, dirs=None, act=Tru'
 
     directories = []
     files = []
+    missing = []
     roots, match, anypats = util.cmdmatcher(repo.root, repo.getcwd(), dirs)
     for src, f, st in repo.dirstate.statwalk(files=roots, match=match,
                                              ignored=True, directories=True):
         if src == 'd':
             directories.append(f)
+        elif src == 'm':
+            missing.append(f)
         elif src == 'f' and f not in repo.dirstate:
             files.append(f)
 
+    _check_missing(ui, repo, missing, force)
+
     directories.sort()
 
     for f in files:
@@ -69,6 +75,43 b' def dopurge(ui, repo, dirs=None, act=Tru'
             ui.note(_('Removing directory %s\n') % f)
             remove(os.rmdir, f)
 
+def _check_missing(ui, repo, missing, force=False):
+    """Abort if there is the chance of having problems with name-mangling fs
+
+    In a name mangling filesystem (e.g. a case insensitive one)
+    dirstate.walk() can yield filenames different from the ones
+    stored in the dirstate. This already confuses the status and
+    add commands, but with purge this may cause data loss.
+    
+    To prevent this, _check_missing will abort if there are missing
+    files. The force option will let the user skip the check if he 
+    knows it is safe.
+    
+    Even with the force option this function will check if any of the 
+    missing files is still available in the working dir: if so there
+    may be some problem with the underlying filesystem, so it
+    aborts unconditionally."""
+
+    found = [f for f in missing if util.lexists(repo.wjoin(f))]
+
+    if found:
+        if not ui.quiet:
+            ui.warn(_("The following tracked files weren't listed by the "
+                      "filesystem, but could still be found:\n"))
+            for f in found:
+                ui.warn("%s\n" % f)
+            if util.checkfolding(repo.path):
+                ui.warn(_("This is probably due to a case-insensitive "
+                          "filesystem\n"))
+        raise util.Abort(_("purging on name mangling filesystems is not "
+                           "yet fully supported"))
+
+    if missing and not force:
+        raise util.Abort(_("there are missing files in the working dir and "
+                           "purge still has problems with them due to name "
+                           "mangling filesystems. "
+                           "Use --force if you know what you are doing"))
+
 
 def purge(ui, repo, *dirs, **opts):
     '''removes files not tracked by mercurial
@@ -100,13 +143,15 b' def purge(ui, repo, *dirs, **opts):'
     if eol == '\0':
         # --print0 implies --print
         act = False
-    dopurge(ui, repo, dirs, act, abort_on_err, eol)
+    force = bool(opts['force'])
+    dopurge(ui, repo, dirs, act, abort_on_err, eol, force)
 
 
 cmdtable = {
     'purge':
         (purge,
          [('a', 'abort-on-err', None, _('abort if an error occurs')),
+          ('f', 'force', None, _('purge even when missing files are detected')),
           ('p', 'print', None, _('print the file names instead of deleting them')),
           ('0', 'print0', None, _('end filenames with NUL, for use with xargs'
                                   ' (implies -p)'))],

tests/test-purge

@@ -74,3 +74,26 b' touch ignored'
 hg purge -p
 hg purge -v
 ls
+
+echo % abort with missing files until we support name mangling filesystems
+touch untracked_file
+rm r1
+# hide error messages to avoid changing the output when the text changes
+hg purge -p 2> /dev/null
+if [ $? -ne 0 ]; then
+    echo "refused to run"
+fi
+if [ -f untracked_file ]; then
+    echo "untracked_file still around"
+fi
+hg purge -p --force
+hg purge -v 2> /dev/null
+if [ $? -ne 0 ]; then
+    echo "refused to run"
+fi
+if [ -f untracked_file ]; then
+    echo "untracked_file still around"
+fi
+hg purge -v --force
+hg revert --all --quiet
+ls

tests/test-purge.out

@@ -47,3 +47,12 b' ignored'
 Removing file ignored
 directory
 r1
+% abort with missing files until we support name mangling filesystems
+refused to run
+untracked_file still around
+untracked_file
+refused to run
+untracked_file still around
+Removing file untracked_file
+directory
+r1