Option to turn off WebDAV file locking

Locking files on WebDAV shares was implemented in tdf#82744,
in particular:

commit 26e6d4b0
    tdf#82744: fix WebDAV lock/unlock behaviour - part 1
commit bc9a8ddb
    tdf#82744: fix WebDAV lock/unlock behaviour - part 2
commit b4576f3d
    tdf#82744: fix WebDAV lock/unlock behaviour - part 3
commit fed29842
    tdf#82744: fix WebDAV lock/unlock behaviour - part 4

Before that, files on WebDAV shares were accessed w/o locking since
the beginning of [OOo] time. This option allows to revert to
the old behaviour i.e. non-locking WebDAV access.

For concurrent read-write WebDAV access by multiple users it is
recommended to keep UseWebDAVFileLocking at default value (true)

Change-Id: Id92177631d4854d6c7bf412164acbd9740db9592
Reviewed-on: https://gerrit.libreoffice.org/64116
Tested-by: Jenkins
Reviewed-by: Thorsten Behrens <Thorsten.Behrens@CIB.de>

officecfg/registry/schema/org/openoffice/Office/Common.xcs

@@ -5356,6 +5356,15 @@
         </info>
         <value>true</value>
       </prop>
+      <prop oor:name="UseWebDAVFileLocking" oor:type="xs:boolean" oor:nillable="false">
+        <info>
+          <desc>Determines if WebDAV-specific file locking is used for documents
+	  on WebDAV shares. It is not recommended to set this option to 'false' in
+	  scenarios where multi-user, concurrent read/write access to WebDAV share
+	  is required</desc>
+        </info>
+        <value>true</value>
+      </prop>
       <prop oor:name="UseDocumentOOoLockFile" oor:type="xs:boolean" oor:nillable="false">
         <info>
           <desc>Allows to specify whether the OOo document file locking

sfx2/source/doc/docfile.cxx

@@ -173,6 +173,11 @@ bool IsLockingUsed()
 
 #endif
 
+bool IsWebDAVLockingUsed()
+{
+    return officecfg::Office::Common::Misc::UseWebDAVFileLocking::get();
+}
+
 /// Gets default attributes of a file:// URL.
 sal_uInt64 GetDefaultFileAttributes(const OUString& rURL)
 {
@@ -1088,6 +1093,10 @@ SfxMedium::LockFileResult SfxMedium::LockOrigFileOnDemand( bool bLoading, bool b
 
     if ( GetURLObject().isAnyKnownWebDAVScheme() )
     {
+        // do nothing if WebDAV locking is disabled
+        if (!IsWebDAVLockingUsed())
+            return LockFileResult::Succeeded;
+
         try
         {
             bool bResult = pImpl->m_bLocked;
@@ -2866,6 +2875,12 @@ void SfxMedium::UnlockFile( bool bReleaseLockStream )
     // check if webdav
     if ( GetURLObject().isAnyKnownWebDAVScheme() )
     {
+        // do nothing if WebDAV locking if disabled
+        // (shouldn't happen because we already skipped locking,
+        // see LockOrigFileOnDemand, but just in case ...)
+        if (!IsWebDAVLockingUsed())
+            return;
+
         if ( pImpl->m_bLocked )
         {
             // an interaction handler should be used for authentication, if needed