1 files changed, 55 insertions, 12 deletions

diff --git a/src/febootstrap_debian.ml b/src/febootstrap_debian.ml
index 23f3593..7482ed4 100644
--- a/src/febootstrap_debian.ml
+++ b/src/febootstrap_debian.ml
@@ -28,6 +28,9 @@ open Febootstrap_cmdline
 (* Create a temporary directory for use by all the functions in this file. *)
 let tmpdir = tmpdir ()
 
+let installed_pkgs =
+  run_command_get_lines "dpkg-query --show --showformat='${Package}\\n'"
+
 let debian_detect () =
   file_exists "/etc/debian_version" &&
     Config.aptitude <> "no" && Config.apt_cache <> "no" && Config.dpkg <> "no"
@@ -51,18 +54,29 @@ let rec debian_resolve_dependencies_and_download names =
         not (List.exists (fun re -> Str.string_match re name 0) excludes)
     ) pkgs in
 
+  let present_pkgs, download_pkgs = List.partition (
+    fun pkg -> List.exists ((=) pkg) installed_pkgs
+  ) pkgs in
+
+  debug "wanted packages (present / download): %s / %s\n"
+    (String.concat " " present_pkgs)
+    (String.concat " " download_pkgs);
+
   (* Download the packages. *)
-  let cmd =
-    sprintf "umask 0000; cd %s && %s download %s"
-      (Filename.quote tmpdir)
-      Config.aptitude
-      (String.concat " " (List.map Filename.quote pkgs)) in
-  run_command cmd;
+  if (List.length download_pkgs > 0)
+  then (
+    let cmd =
+      sprintf "umask 0000; cd %s && %s download %s"
+        (Filename.quote tmpdir)
+        Config.aptitude
+        (String.concat " " (List.map Filename.quote download_pkgs)) in
+    run_command cmd
+  );
 
   (* Find out what aptitude downloaded. *)
   let files = Sys.readdir tmpdir in
 
-  let pkgs = List.map (
+  let download_pkgs = List.map (
     fun pkg ->
       (* Look for 'pkg_*.deb' in the list of files. *)
       let pre = pkg ^ "_" in
@@ -79,9 +93,9 @@ let rec debian_resolve_dependencies_and_download names =
 	exit 1
       with
 	  Exit -> !r
-  ) pkgs in
+  ) download_pkgs in
 
-  List.sort compare pkgs
+  List.sort compare (List.append present_pkgs download_pkgs)
 
 (* On Ubuntu 10.04 LTS, apt-cache depends --recurse is broken.  It
  * doesn't return the full list of dependencies.  Therefore recurse
@@ -106,7 +120,7 @@ and workaround_broken_apt_cache_depends_recurse names =
   else
     names
 
-let debian_list_files pkg =
+let debian_list_files_downloaded pkg =
   debug "unpacking %s ..." pkg;
 
   (* We actually need to extract the file in order to get the
@@ -147,9 +161,38 @@ let debian_list_files pkg =
 
   files
 
+let debian_list_files_installed pkg =
+  debug "using installed package %s ..." pkg;
+  let cmd = sprintf "dpkg-query --listfiles %s" pkg in
+  let lines = run_command_get_lines cmd in
+  (* filter out lines not directly describing fs objects such as
+     "package diverts others to: /path/to/..." *)
+  let lines = List.filter (
+    fun l -> l.[0] = '/' && l.[1] != '.'
+  ) lines in
+  let files = List.map (
+    fun path ->
+      let statbuf = lstat path in
+      let is_dir = statbuf.st_kind = S_DIR in
+      let config = statbuf.st_kind = S_REG && string_prefix "/etc/" path in
+      let mode = statbuf.st_perm in
+      (path, { ft_dir = is_dir; ft_config = config; ft_mode = mode;
+	       ft_ghost = false; ft_size = statbuf.st_size })
+  ) lines in
+  files
+
+let debian_list_files ?(use_installed=false) pkg =
+  if use_installed && List.exists ((=) pkg) installed_pkgs then
+    debian_list_files_installed pkg
+  else
+    debian_list_files_downloaded pkg
+
 (* Easy because we already unpacked the archive above. *)
-let debian_get_file_from_package pkg file =
-  tmpdir // pkg ^ ".d" // file
+let debian_get_file_from_package ?(use_installed=false) pkg file =
+  if use_installed && List.exists (fun p -> p = pkg) installed_pkgs then
+    file
+  else
+    tmpdir // pkg ^ ".d" // file
 
 let () =
   let ph = {