* apt-pkg/contrib/fileutl.{cc,h}:

  - add GetModificationTime() helper
* apt-pkg/pkgcachegen.cc:
  - regenerate the cache if the sources.list changes to ensure
    that changes in the ordering there will be honored by apt
* apt-pkg/sourcelist.{cc,h}:
  - add pkgSourceList::GetLastModifiedTime() helper

apt-pkg/contrib/fileutl.cc

@@ -446,6 +446,17 @@ string SafeGetCWD()
    return S;
 }
 									/*}}}*/
+// GetModificationTime - Get the mtime of the given file or -1 on error /*{{{*/
+// ---------------------------------------------------------------------
+/* We return / on failure. */
+time_t GetModificationTime(string const &Path)
+{
+   struct stat St;
+   if (stat(Path.c_str(), &St) < 0)
+      return -1;
+   return  St.st_mtime;
+}
+									/*}}}*/
 // flNotDir - Strip the directory from the filename			/*{{{*/
 // ---------------------------------------------------------------------
 /* */

apt-pkg/contrib/fileutl.h

@@ -97,6 +97,7 @@ bool FileExists(string File);
 bool RealFileExists(string File);
 bool DirectoryExists(string const &Path) __attrib_const;
 bool CreateDirectory(string const &Parent, string const &Path);
+time_t GetModificationTime(string const &Path);
 
 /** \brief Ensure the existence of the given Path
  *

apt-pkg/pkgcachegen.cc

@@ -915,8 +915,11 @@ unsigned long pkgCacheGenerator::WriteUniqString(const char *S,
 /* This just verifies that each file in the list of index files exists,
    has matching attributes with the cache and the cache does not have
    any extra files. */
-static bool CheckValidity(const string &CacheFile, FileIterator Start, 
-                          FileIterator End,MMap **OutMap = 0)
+static bool CheckValidity(const string &CacheFile, 
+                          pkgSourceList &List,
+                          FileIterator Start, 
+                          FileIterator End,
+                          MMap **OutMap = 0)
 {
    bool const Debug = _config->FindB("Debug::pkgCacheGen", false);
    // No file, certainly invalid
@@ -927,6 +930,13 @@ static bool CheckValidity(const string &CacheFile, FileIterator Start,
       return false;
    }
 
+   if (List.GetLastModifiedTime() < GetModificationTime(CacheFile))
+   {
+      if (Debug == true)
+	 std::clog << "sources.list is newer than the cache" << std::endl;
+      return false;
+   }
+
    // Map it
    FileFd CacheF(CacheFile,FileFd::ReadOnly);
    SPtr<MMap> Map = new MMap(CacheF,0);
@@ -1152,7 +1162,7 @@ bool pkgCacheGenerator::MakeStatusCache(pkgSourceList &List,OpProgress *Progress
       Progress->OverallProgress(0,1,1,_("Reading package lists"));
 
    // Cache is OK, Fin.
-   if (CheckValidity(CacheFile,Files.begin(),Files.end(),OutMap) == true)
+   if (CheckValidity(CacheFile, List, Files.begin(),Files.end(),OutMap) == true)
    {
       if (Progress != NULL)
 	 Progress->OverallProgress(1,1,1,_("Reading package lists"));
@@ -1189,7 +1199,7 @@ bool pkgCacheGenerator::MakeStatusCache(pkgSourceList &List,OpProgress *Progress
    // Lets try the source cache.
    unsigned long CurrentSize = 0;
    unsigned long TotalSize = 0;
-   if (CheckValidity(SrcCacheFile,Files.begin(),
+   if (CheckValidity(SrcCacheFile, List, Files.begin(),
 		     Files.begin()+EndOfSource) == true)
    {
       if (Debug == true)

apt-pkg/sourcelist.cc

@@ -341,4 +341,22 @@ bool pkgSourceList::ReadSourceDir(string Dir)
 
 }
 									/*}}}*/
+// GetLastModified()						/*{{{*/
+// ---------------------------------------------------------------------
+/* */
+time_t pkgSourceList::GetLastModifiedTime()
+{
+   // go over the parts
+   string Main = _config->FindFile("Dir::Etc::sourcelist");
+   string Parts = _config->FindDir("Dir::Etc::sourceparts");
+   vector<string> const List = GetListOfFilesInDir(Parts, "list", true);
+
+   // calculate the time
+   time_t mtime_sources = GetModificationTime(Main);
+   for (vector<string>::const_iterator I = List.begin(); I != List.end(); I++)
+      mtime_sources = std::max(mtime_sources, GetModificationTime(*I));
+
+   return mtime_sources;
+}
+									/*}}}*/
 

apt-pkg/sourcelist.h

@@ -92,6 +92,9 @@ class pkgSourceList
 		  pkgIndexFile *&Found) const;
    bool GetIndexes(pkgAcquire *Owner, bool GetAll=false) const;
    
+   // query last-modified time
+   time_t GetLastModifiedTime();
+
    pkgSourceList();
    pkgSourceList(string File);
    ~pkgSourceList();      

debian/changelog

@@ -10,6 +10,13 @@ apt (0.8.15.2) unstable; urgency=high
     - add new DeEscapeString() similar to DeQuoteString but
       unescape character escapes like \0XX and \xXX (plus added
       test)
+  * apt-pkg/contrib/fileutl.{cc,h}:
+    - add GetModificationTime() helper
+  * apt-pkg/pkgcachegen.cc:
+    - regenerate the cache if the sources.list changes to ensure
+      that changes in the ordering there will be honored by apt
+  * apt-pkg/sourcelist.{cc,h}:
+    - add pkgSourceList::GetLastModifiedTime() helper
 
  -- Michael Vogt <mvo@debian.org>  Tue, 12 Jul 2011 11:54:47 +0200