Improve and test distclean implementation

The implementation as-is as various smaller/esoteric bugs and
inconsistencies like apt-get not supporting them, the option -s
being supported in code but not accepted on the command line,
the regex not escaping the dot before the file extension and
exposing more implementation details to public headers than we
actually need.

Also comes with a small test case to ensure it actually works.

References: bd7c126e3fb1b94e76e0e632c657cea854586844

2 files changed, 12 insertions, 29 deletions

diff --git a/apt-pkg/acquire.cc b/apt-pkg/acquire.cc
index 727880e71..1cb55bf14 100644
--- a/apt-pkg/acquire.cc
+++ b/apt-pkg/acquire.cc
@@ -826,11 +826,11 @@ pkgAcquire::Worker *pkgAcquire::WorkerStep(Worker *I)
    return I->NextAcquire;
 }
 									/*}}}*/
-// Acquire::CleanDir - Cleans a directory					/*{{{*/
+// CleanDir - Cleans a directory					/*{{{*/
 // ---------------------------------------------------------------------
 /* This is a bit simplistic, it looks at every file in the dir and sees
    if it matches the predicate or not. */
-bool pkgAcquire::CleanDir(string Dir, std::function<bool(char const*)> const &Keep, char const * const Caller)
+static bool CleanDir(std::string const &Dir, std::function<bool(std::string_view)> const &Keep, char const * const Caller)
 {
    // non-existing directories are by definition clean…
    if (DirectoryExists(Dir) == false)
@@ -855,7 +855,7 @@ bool pkgAcquire::CleanDir(string Dir, std::function<bool(char const*)> const &Ke
 	  strcmp(E->d_name, "lost+found") == 0 ||
 	  strcmp(E->d_name, ".") == 0 ||
 	  strcmp(E->d_name, "..") == 0 ||
-	  Keep(E->d_name) == true)
+	  Keep(E->d_name))
 	 continue;
       RemoveFileAt(Caller, dirfd, E->d_name);
    }
@@ -867,12 +867,12 @@ bool pkgAcquire::CleanDir(string Dir, std::function<bool(char const*)> const &Ke
 // ---------------------------------------------------------------------
 /* This is a bit simplistic, it looks at every file in the dir and sees
    if it is part of the download set. */
-bool pkgAcquire::Clean(string Dir)
+bool pkgAcquire::Clean(std::string Dir)
 {
    return CleanDir(
       Dir,
       // Look in the get list and if found then keep
-      [this](char const *FName) {
+      [this](std::string_view const FName) {
          return std::any_of(Items.cbegin(), Items.cend(),
             [FName](pkgAcquire::Item const * const I) {
                return flNotDir(I->DestFile) == FName;
@@ -882,21 +882,19 @@ bool pkgAcquire::Clean(string Dir)
    );
 }
                            /*}}}*/
-// Acquire::CleanLists - Cleans a directory of list files             /*{{{*/
-// ---------------------------------------------------------------------
-/* */
-bool pkgAcquire::CleanLists(string Dir)
+// Acquire::CleanLists - Cleans a directory of list files		/*{{{*/
+bool pkgAcquire::CleanLists(std::string const &Dir)
 {
+   std::regex const KeepPattern(".*_(Release|Release\\.gpg|InRelease)");
    return CleanDir(
       Dir,
-      [](char const *FName) noexcept {
-         static const std::regex KeepPattern(".*_(Release|Release.gpg|InRelease)");
-         return std::regex_match(FName, KeepPattern);
+      [&KeepPattern](std::string_view const FName) noexcept {
+         return std::regex_match(FName.begin(), FName.end(), KeepPattern);
       },
       "pkgAcquire::CleanLists"
    );
 }
-                           /*}}}*/
+									/*}}}*/
 // Acquire::TotalNeeded - Number of bytes to fetch			/*{{{*/
 // ---------------------------------------------------------------------
 /* This is the total number of bytes needed */
diff --git a/apt-pkg/acquire.h b/apt-pkg/acquire.h
index a5f7a40c8..f7c40aa5f 100644
--- a/apt-pkg/acquire.h
+++ b/apt-pkg/acquire.h
@@ -70,7 +70,6 @@
 #include <apt-pkg/weakptr.h>
 
 #include <chrono>
-#include <functional>
 #include <string>
 #include <vector>
 
@@ -338,7 +337,7 @@ class APT_PUBLIC pkgAcquire
     *
     *  \return \b true if the directory exists and is readable.
     */
-   bool CleanLists(std::string Dir);
+   bool CleanLists(std::string const &Dir);
 
    /** \return the total size in bytes of all the items included in
     *  this download.
@@ -381,20 +380,6 @@ class APT_PUBLIC pkgAcquire
 
    private:
    APT_HIDDEN void Initialize();
-
-   /** Delete each entry in the given directory whose name does \em not match
-    *  a criterion.
-    *
-    *  \param Dir The directory to be cleaned.
-    *
-    *  \param KeepP A predicate telling to keep the named file; if it is
-    *  non-empty and returns true, the file is kept.
-    *
-    *  \param Caller Log name of the caller.
-    *
-    *  \return \b true if the directory exists and is readable.
-    */
-   APT_HIDDEN static bool CleanDir(std::string Dir, std::function<bool(char const*)> const &KeepP, char const * const Caller);
 };
 
 /** \brief Represents a single download source from which an item