Fix handling of linked rename chains in incremental backups

* src/incremen.c: Change the meaning of the DIRF_RENAMED flag.  Now it
marks a directory which is the last one in a chain of renames.
Regular renamed directories are recognized by their orig member being
non-NULL.  Directories marked with DIRF_RENAMED start encoding of renames.
(procdir): Clear DIRF_RENAMED flag on directories which are origins for
renames.
(makedumpdir): Use the orig member to check if the directory is a
result of a rename.
(store_rename): Move the check for DIR_IS_RENAMED to the caller. Don't
clear the DIRF_RENAMED, it is not needed any more.

* tests/rename06.at: New test.
* tests/Makefile.am: Add rename06.at
* tests/testsuite.at: Likewise.

src/incremen.c

@@ -38,7 +38,15 @@ enum children
 #define DIRF_FOUND    0x0004    /* directory is found on fs */
 #define DIRF_NEW      0x0008    /* directory is new (not found
 				   in the previous dump) */
-#define DIRF_RENAMED  0x0010    /* directory is renamed */
+#define DIRF_RENAMED  0x0010    /* Last target in a chain of renames */
+/* A directory which is renamed from another one is recognized by its
+   orig member, which is not-NULL.  This directory may eventually be
+   the source for another rename, in which case it will be pointed to by
+   the orig member of another directory structure.  The last directory
+   in such a chain of renames (the one which is not pointed to by any
+   other orig) is marked with the DIRF_RENAMED flag.  This marks a starting
+   point from which append_incremental_renames starts encoding renames for
+   this chain. */
 
 #define DIR_IS_INITED(d) ((d)->flags & DIRF_INIT)
 #define DIR_IS_NFS(d) ((d)->flags & DIRF_NFS)
@@ -495,6 +503,7 @@ procdir (const char *name_buffer, struct tar_stat_info *st,
 			    quote_n (1, d->name)));
 		  directory->orig = d;
 		  DIR_SET_FLAG (directory, DIRF_RENAMED);
+		  DIR_CLEAR_FLAG (d, DIRF_RENAMED);
 		  dirlist_replace_prefix (d->name, name_buffer);
 		}
 	      directory->children = CHANGED_CHILDREN;
@@ -537,6 +546,7 @@ procdir (const char *name_buffer, struct tar_stat_info *st,
 			quote_n (1, d->name)));
 	      directory->orig = d;
 	      DIR_SET_FLAG (directory, DIRF_RENAMED);
+	      DIR_CLEAR_FLAG (d, DIRF_RENAMED);
 	      dirlist_replace_prefix (d->name, name_buffer);
 	    }
 	  directory->children = CHANGED_CHILDREN;
@@ -649,7 +659,7 @@ makedumpdir (struct directory *directory, const char *dir)
 
   if (directory->children == ALL_CHILDREN)
     dump = NULL;
-  else if (DIR_IS_RENAMED (directory))
+  else if (directory->orig)
     dump = directory->orig->idump ?
            directory->orig->idump : directory->orig->dump;
   else
@@ -878,44 +888,36 @@ obstack_code_rename (struct obstack *stk, char const *from, char const *to)
 static void
 store_rename (struct directory *dir, struct obstack *stk)
 {
-  if (DIR_IS_RENAMED (dir))
-    {
-      struct directory *prev, *p;
-
-      /* Detect eventual cycles and clear DIRF_RENAMED flag, so these entries
-	 are ignored when hit by this function next time.
-	 If the chain forms a cycle, prev points to the entry DIR is renamed
-	 from. In this case it still retains DIRF_RENAMED flag, which will be
-	 cleared in the 'else' branch below */
-      for (prev = dir; prev && prev->orig != dir; prev = prev->orig)
-	DIR_CLEAR_FLAG (prev, DIRF_RENAMED);
-
-      if (prev == NULL)
-	{
-	  for (p = dir; p && p->orig; p = p->orig)
-	    obstack_code_rename (stk, p->orig->name, p->name);
-	}
-      else
-	{
-	  char *temp_name;
-
-	  DIR_CLEAR_FLAG (prev, DIRF_RENAMED);
+  struct directory *prev, *p;
 
-	  /* Break the cycle by using a temporary name for one of its
-	     elements.
-	     First, create a temp name stub entry. */
-	  temp_name = dir_name (dir->name);
-	  obstack_1grow (stk, 'X');
-	  obstack_grow (stk, temp_name, strlen (temp_name) + 1);
+  /* Detect eventual cycles. If the chain forms a cycle, prev points to
+     the entry DIR is renamed from.*/
+  for (prev = dir; prev && prev->orig != dir; prev = prev->orig)
+    ;
 
-	  obstack_code_rename (stk, dir->name, "");
-
-	  for (p = dir; p != prev; p = p->orig)
-	    obstack_code_rename (stk, p->orig->name, p->name);
-
-	  obstack_code_rename (stk, "", prev->name);
-	  free (temp_name);
-	}
+  if (prev == NULL)
+    {
+      for (p = dir; p && p->orig; p = p->orig)
+	obstack_code_rename (stk, p->orig->name, p->name);
+    }
+  else
+    {
+      char *temp_name;
+      
+      /* Break the cycle by using a temporary name for one of its
+	 elements.
+	 First, create a temp name stub entry. */
+      temp_name = dir_name (dir->name);
+      obstack_1grow (stk, 'X');
+      obstack_grow (stk, temp_name, strlen (temp_name) + 1);
+      
+      obstack_code_rename (stk, dir->name, "");
+      
+      for (p = dir; p != prev; p = p->orig)
+	obstack_code_rename (stk, p->orig->name, p->name);
+      
+      obstack_code_rename (stk, "", prev->name);
+      free (temp_name);
     }
 }
 
@@ -941,7 +943,8 @@ append_incremental_renames (struct directory *dir)
     size = 0;
 
   for (dp = dirhead; dp; dp = dp->next)
-    store_rename (dp, &stk);
+    if (DIR_IS_RENAMED (dp))
+      store_rename (dp, &stk);
 
   /* FIXME: Is this the right thing to do when DIR is null?  */
   if (dir && obstack_object_size (&stk) != size)

tests/Makefile.am

@@ -200,6 +200,7 @@ TESTSUITE_AT = \
  rename03.at\
  rename04.at\
  rename05.at\
+ rename06.at\
  remfiles01.at\
  remfiles02.at\
  remfiles03.at\

tests/rename06.at

@@ -0,0 +1,88 @@
+# Test suite for GNU tar.
+# Copyright 2020 Free Software Foundation, Inc.
+#
+# This file is part of GNU tar.
+#
+# GNU tar is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# GNU tar is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+AT_SETUP([chained renames])
+AT_KEYWORDS([incremental rename06 rename])
+
+# Description: test whether chained renames are processed correctly
+# during the incremental archive creation.  Tar 1.32.90 failed to
+# encode them.
+# Reported by: Deweloper <deweloper@wp.pl>
+# References: <20200214100922.44c43334@amazur-u.kat.adbgroup.pl>,
+#   https://lists.gnu.org/archive/html/bug-tar/2020-02/msg00008.html
+
+AT_TAR_CHECK([
+AT_SORT_PREREQ
+decho Creating directory structure
+mkdir test test/d1 test/d2
+genfile --file test/d1/file1
+genfile --file test/d2/file2
+
+decho First dump
+tar -c -g 0.snar -C test -f backup0.tar .
+
+decho Altering directory structure
+genfile --file test/d2/file3
+mv test/d1 test/d3
+mv test/d2 test/d1
+
+decho Second dump
+cp 0.snar 1.snar
+tar -vc -g 1.snar -C test -f backup1.tar .
+
+mkdir test1
+
+decho First extract
+tar -C test1 -x -g /dev/null -f backup0.tar
+
+decho Second extract
+tar -C test1 -x -g /dev/null -f backup1.tar
+
+decho Resulting directory
+find test1 | sort
+],
+[0],
+[Creating directory structure
+First dump
+Altering directory structure
+Second dump
+./
+./d1/
+./d3/
+./d1/file3
+First extract
+Second extract
+Resulting directory
+test1
+test1/d1
+test1/d1/file2
+test1/d1/file3
+test1/d3
+test1/d3/file1
+],
+[Creating directory structure
+First dump
+Altering directory structure
+Second dump
+tar: ./d1: Directory has been renamed from './d2'
+tar: ./d3: Directory has been renamed from './d1'
+First extract
+Second extract
+Resulting directory
+],[],[],[gnu, oldgnu, posix])
+AT_CLEANUP

tests/testsuite.at

@@ -390,6 +390,7 @@ m4_include([rename02.at])
 m4_include([rename03.at])
 m4_include([rename04.at])
 m4_include([rename05.at])
+m4_include([rename06.at])
 m4_include([chtype.at])
 
 AT_BANNER([Ignore failing reads])