Fix the newly introduced method GetListOfFilesInDir to not accept every

file if no extension is enforced (= restore old behaviour). (Closes: #565213)

This commit includes also:
* apt-pkg/policy.cc:
  - accept also partfiles with "pref" file extension as valid
* apt-pkg/contrib/configuration.cc:
  - accept also partfiles with "conf" file extension as valid
* doc/apt.conf.5.xml:
  - reorder description and split out syntax
  - add partfile name convention (Closes: #558348)
* doc/apt_preferences.conf.5.xml:
  - describe partfile name convention also here

And a lovely test application of course.

4 files changed, 86 insertions, 7 deletions

diff --git a/apt-pkg/contrib/configuration.cc b/apt-pkg/contrib/configuration.cc
index 80b089fac..7588b041c 100644
--- a/apt-pkg/contrib/configuration.cc
+++ b/apt-pkg/contrib/configuration.cc
@@ -832,7 +832,7 @@ bool ReadConfigFile(Configuration &Conf,const string &FName,bool const &AsSectio
 bool ReadConfigDir(Configuration &Conf,const string &Dir,
 		   bool const &AsSectional, unsigned const &Depth)
 {
-   vector<string> const List = GetListOfFilesInDir(Dir, "", true);
+   vector<string> const List = GetListOfFilesInDir(Dir, "conf", true, true);
 
    // Read the files
    for (vector<string>::const_iterator I = List.begin(); I != List.end(); I++)
diff --git a/apt-pkg/contrib/fileutl.cc b/apt-pkg/contrib/fileutl.cc
index cce8a4512..da32983f1 100644
--- a/apt-pkg/contrib/fileutl.cc
+++ b/apt-pkg/contrib/fileutl.cc
@@ -202,8 +202,37 @@ bool FileExists(string File)
 /* If an extension is given only files with this extension are included
    in the returned vector, otherwise every "normal" file is included. */
 std::vector<string> GetListOfFilesInDir(string const &Dir, string const &Ext,
-					bool const &SortList) 
+					bool const &SortList)
 {
+   return GetListOfFilesInDir(Dir, Ext, SortList, false);
+}
+std::vector<string> GetListOfFilesInDir(string const &Dir, string const &Ext,
+					bool const &SortList, bool const &AllowNoExt)
+{
+   std::vector<string> ext;
+   ext.reserve(2);
+   if (Ext.empty() == false)
+      ext.push_back(Ext);
+   if (AllowNoExt == true && ext.empty() == false)
+      ext.push_back("");
+   return GetListOfFilesInDir(Dir, ext, SortList);
+}
+std::vector<string> GetListOfFilesInDir(string const &Dir, std::vector<string> const &Ext,
+					bool const &SortList)
+{
+   // Attention debuggers: need to be set with the environment config file!
+   bool const Debug = _config->FindB("Debug::GetListOfFilesInDir", false);
+   if (Debug == true)
+   {
+      std::clog << "Accept in " << Dir << " only files with the following " << Ext.size() << " extensions:" << std::endl;
+      if (Ext.empty() == true)
+	 std::clog << "\tNO extension" << std::endl;
+      else
+	 for (std::vector<string>::const_iterator e = Ext.begin();
+	      e != Ext.end(); ++e)
+	    std::clog << '\t' << (e->empty() == true ? "NO" : *e) << " extension" << std::endl;
+   }
+
    std::vector<string> List;
    DIR *D = opendir(Dir.c_str());
    if (D == 0) 
@@ -214,28 +243,73 @@ std::vector<string> GetListOfFilesInDir(string const &Dir, string const &Ext,
 
    for (struct dirent *Ent = readdir(D); Ent != 0; Ent = readdir(D)) 
    {
+      // skip "hidden" files
       if (Ent->d_name[0] == '.')
 	 continue;
 
-      if (Ext.empty() == false && flExtension(Ent->d_name) != Ext)
-	 continue;
+      // check for accepted extension:
+      // no extension given -> periods are bad as hell!
+      // extensions given -> "" extension allows no extension
+      if (Ext.empty() == false)
+      {
+	 string d_ext = flExtension(Ent->d_name);
+	 if (d_ext == Ent->d_name) // no extension
+	 {
+	    if (std::find(Ext.begin(), Ext.end(), "") == Ext.end())
+	    {
+	       if (Debug == true)
+		  std::clog << "Bad file: " << Ent->d_name << " → no extension" << std::endl;
+	       continue;
+	    }
+	 }
+	 else if (std::find(Ext.begin(), Ext.end(), d_ext) == Ext.end())
+	 {
+	    if (Debug == true)
+	       std::clog << "Bad file: " << Ent->d_name << " → bad extension »" << flExtension(Ent->d_name) << "«" << std::endl;
+	    continue;
+	 }
+      }
 
-      // Skip bad file names ala run-parts
+      // Skip bad filenames ala run-parts
       const char *C = Ent->d_name;
       for (; *C != 0; ++C)
 	 if (isalpha(*C) == 0 && isdigit(*C) == 0
-	     && *C != '_' && *C != '-' && *C != '.')
+	     && *C != '_' && *C != '-') {
+	    // no required extension -> dot is a bad character
+	    if (*C == '.' && Ext.empty() == false)
+	       continue;
 	    break;
+	 }
 
+      // we don't reach the end of the name -> bad character included
       if (*C != 0)
+      {
+	 if (Debug == true)
+	    std::clog << "Bad file: " << Ent->d_name << " → bad character »"
+	       << *C << "« in filename (period allowed: " << (Ext.empty() ? "no" : "yes") << ")" << std::endl;
 	 continue;
+      }
+
+      // skip filenames which end with a period. These are never valid
+      if (*(C - 1) == '.')
+      {
+	 if (Debug == true)
+	    std::clog << "Bad file: " << Ent->d_name << " → Period as last character" << std::endl;
+	 continue;
+      }
 
       // Make sure it is a file and not something else
       string const File = flCombine(Dir,Ent->d_name);
       struct stat St;
       if (stat(File.c_str(),&St) != 0 || S_ISREG(St.st_mode) == 0)
+      {
+	 if (Debug == true)
+	    std::clog << "Bad file: " << Ent->d_name << " → stat says not a good file" << std::endl;
 	 continue;
+      }
 
+      if (Debug == true)
+	 std::clog << "Accept file: " << Ent->d_name << " in " << Dir << std::endl;
       List.push_back(File);
    }
    closedir(D);
diff --git a/apt-pkg/contrib/fileutl.h b/apt-pkg/contrib/fileutl.h
index 2807c29d9..85a94898c 100644
--- a/apt-pkg/contrib/fileutl.h
+++ b/apt-pkg/contrib/fileutl.h
@@ -82,8 +82,13 @@ bool RunScripts(const char *Cnf);
 bool CopyFile(FileFd &From,FileFd &To);
 int GetLock(string File,bool Errors = true);
 bool FileExists(string File);
+// FIXME: next ABI-Break: merge the two method-headers
 std::vector<string> GetListOfFilesInDir(string const &Dir, string const &Ext,
 					bool const &SortList);
+std::vector<string> GetListOfFilesInDir(string const &Dir, string const &Ext,
+					bool const &SortList, bool const &AllowNoExt);
+std::vector<string> GetListOfFilesInDir(string const &Dir, std::vector<string> const &Ext,
+					bool const &SortList);
 string SafeGetCWD();
 void SetCloseExec(int Fd,bool Close);
 void SetNonBlock(int Fd,bool Block);
diff --git a/apt-pkg/policy.cc b/apt-pkg/policy.cc
index 393181b6d..f9901bc9a 100644
--- a/apt-pkg/policy.cc
+++ b/apt-pkg/policy.cc
@@ -280,7 +280,7 @@ bool ReadPinDir(pkgPolicy &Plcy,string Dir)
       return true;
    }
 
-   vector<string> const List = GetListOfFilesInDir(Dir, "", true);
+   vector<string> const List = GetListOfFilesInDir(Dir, "pref", true, true);
 
    // Read the files
    for (vector<string>::const_iterator I = List.begin(); I != List.end(); I++)