do not redownload unchanged InRelease files

Before we download the 'new' InRelease file the old file will be moved
out of the way with the name 'foobar_InRelease.reverify', so if no
partial file for the 'new' file exists take the modification time from
this reverify file, so that if we get an IMS hit for the InRelease file
we can move back the reverify file as new file rather than downloading
the 'new' file even though we already have it.

We do the same for Release files and this happened to work until the
reverify renaming was corrected for InRelease files.

apt-pkg/acquire-item.cc

@@ -1289,7 +1289,14 @@ void pkgAcqMetaIndex::RetrievalDone(string Message)			/*{{{*/
       string FinalFile = _config->FindDir("Dir::State::lists");
       FinalFile += URItoFileName(RealURI);
       if (SigFile == DestFile)
+      {
 	 SigFile = FinalFile;
+	 // constructor of pkgAcqMetaClearSig moved it out of the way,
+	 // now move it back in on IMS hit for the 'old' file
+	 string const OldClearSig = DestFile + ".reverify";
+	 if (RealFileExists(OldClearSig) == true)
+	    Rename(OldClearSig, FinalFile);
+      }
       DestFile = FinalFile;
    }
    Complete = true;
@@ -1595,7 +1602,11 @@ string pkgAcqMetaClearSig::Custom600Headers()
 
    struct stat Buf;
    if (stat(Final.c_str(),&Buf) != 0)
-      return "\nIndex-File: true\nFail-Ignore: true\n";
+   {
+      Final = DestFile + ".reverify";
+      if (stat(Final.c_str(),&Buf) != 0)
+	 return "\nIndex-File: true\nFail-Ignore: true\n";
+   }
 
    return "\nIndex-File: true\nFail-Ignore: true\nLast-Modified: " + TimeRFC1123(Buf.st_mtime);
 }

debian/changelog

@@ -19,6 +19,7 @@ apt (0.9.8.3) UNRELEASED; urgency=low
   * handle missing "Description" in apt-cache show (Closes: #712435)
   * try defaults if auto-detection failed in apt-cdrom (Closes: #712433)
   * support \n and \r\n line endings in ReadMessages
+  * do not redownload unchanged InRelease files
 
  -- David Kalnischkies <kalnischkies@gmail.com>  Sun, 09 Jun 2013 15:06:24 +0200