commit 21a41318650adf10187f8c3d0be6a05a40f7cb67
Author:     Simon Howard <fraggle@gmail.com>
AuthorDate: Tue Oct 21 00:54:19 2014 -0400
Commit:     Simon Howard <fraggle@gmail.com>
CommitDate: Tue Oct 21 00:54:19 2014 -0400

    doom: Add -pack parameter to specify mission pack.

    The main purpose for this parameter is to allow mods made for the Final
    Doom IWADs to be played properly with Freedoom. Chocolate Doom detects
    mission packs (pack_tnt/pack_plut) based on the file name. However, the
    Freedoom: Phase 2 IWAD contains the textures for all three Doom2-format
    IWADs, so can be used to play MegaWADs like Plutonia 2 that were
    designed to be played with plutonia.wad.

    Because mission pack detection is done based on filename, freedoom2.wad
    is handled the same as doom2.wad (a sensible default). But this means that
    when playing using a mod like Plutonia 2, the wrong level name is shown
    on the automap screen (along with eg. intermission text). To fix this we
    need a way to manually override the mission pack. -pack allows this to
    be done. It's kind of tedious that this has to be done manually but at
    least it can be done.

    Thanks chungy for the bug report/suggestion. This fixes #449.
---
 src/doom/d_main.c | 52 +++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 51 insertions(+), 1 deletion(-)

diff --git a/src/doom/d_main.c b/src/doom/d_main.c
index c7987b90..d2520c5d 100644
--- a/src/doom/d_main.c
+++ b/src/doom/d_main.c
@@ -681,6 +681,38 @@ static char *GetGameName(char *gamename)
     return gamename;
 }

+static void SetMissionForPackName(char *pack_name)
+{
+    int i;
+    static const struct
+    {
+        char *name;
+        int mission;
+    } packs[] = {
+        { "doom2",    doom2 },
+        { "tnt",      pack_tnt },
+        { "plutonia", pack_plut },
+    };
+
+    for (i = 0; i < arrlen(packs); ++i)
+    {
+        if (!strcasecmp(pack_name, packs[i].name))
+        {
+            gamemission = packs[i].mission;
+            return;
+        }
+    }
+
+    printf("Valid mission packs are:\n");
+
+    for (i = 0; i < arrlen(packs); ++i)
+    {
+        printf("\t%s\n", packs[i].name);
+    }
+
+    I_Error("Unknown mission pack name: %s", pack_name);
+}
+
 //
 // Find out what version of Doom is playing.
 //
@@ -742,9 +774,27 @@ void D_IdentifyVersion(void)
     }
     else
     {
-        // Doom 2 of some kind.
+        int p;

+        // Doom 2 of some kind.
         gamemode = commercial;
+
+        // We can manually override the gamemission that we got from the
+        // IWAD detection code. This allows us to eg. play Plutonia 2
+        // with Freedoom and get the right level names.
+
+        //!
+        // @arg <pack>
+        //
+        // Explicitly specify a Doom II "mission pack" to run as, instead of
+        // detecting it based on the filename. Valid values are: "doom2",
+        // "tnt" and "plutonia".
+        //
+        p = M_CheckParmWithArgs("-pack", 1);
+        if (p > 0)
+        {
+            SetMissionForPackName(myargv[p + 1]);
+        }
     }
 }