Add 'debug' option which preserves failed package dirs (#119)

If a package fails to install, it is normally deleted to prevent stale
packages from clogging up the system. But for debugging the failure it
is useful to keep the package around.

gap/PackageManager.gi

@@ -291,13 +291,17 @@ function(url)
   # Install dependencies
   if PKGMAN_InstallDependencies(dir) <> true then
     Info(InfoPackageManager, 1, "Dependencies not satisfied for ", topdir);
-    PKGMAN_RemoveDir(dir);
+    if ValueOption("debug") <> true then
+      PKGMAN_RemoveDir(dir);
+    fi;
     return false;
   fi;
 
   # Check validity
   if PKGMAN_CheckPackage(dir) = false then
-    PKGMAN_RemoveDir(dir);
+    if ValueOption("debug") <> true then
+      PKGMAN_RemoveDir(dir);
+    fi;
     return false;
   fi;
   PKGMAN_RefreshPackageInfo();
@@ -380,14 +384,18 @@ function(url, args...)
   info := Filename(Directory(dir), "PackageInfo.g");
   if not IsReadableFile(info) then
     Info(InfoPackageManager, 1, "Could not find PackageInfo.g");
-    PKGMAN_RemoveDir(dir);
+    if ValueOption("debug") <> true then
+      PKGMAN_RemoveDir(dir);
+    fi;
     return false;
   fi;
 
   # Install dependencies
   if PKGMAN_InstallDependencies(dir) <> true then
     Info(InfoPackageManager, 1, "Dependencies not satisfied for ", name);
-    PKGMAN_RemoveDir(dir);
+    if ValueOption("debug") <> true then
+      PKGMAN_RemoveDir(dir);
+    fi;
     return false;
   fi;
 
@@ -470,14 +478,18 @@ function(url, args...)
   info := Filename(Directory(dir), "PackageInfo.g");
   if not IsReadableFile(info) then
     Info(InfoPackageManager, 1, "Could not find PackageInfo.g");
-    PKGMAN_RemoveDir(dir);
+    if ValueOption("debug") <> true then
+      PKGMAN_RemoveDir(dir);
+    fi;
     return false;
   fi;
 
   # Install dependencies
   if PKGMAN_InstallDependencies(dir) <> true then
     Info(InfoPackageManager, 1, "Dependencies not satisfied for ", name);
-    PKGMAN_RemoveDir(dir);
+    if ValueOption("debug") <> true then
+      PKGMAN_RemoveDir(dir);
+    fi;
     return false;
   fi;