Add a commit-msg hook lint and various other cleanups

Turns out that gitlint by default enforces the exact commit-msg format that I
like to use. I'm enabling this because even I write poor commit messages
sometimes, and looking back on my commits from even a few days ago is sometimes
not very helpful.

I also made some minor comment and nix changes that I noticed while reviewing my
work from the last few days.

2 files changed, 15 insertions, 11 deletions

diff --git a/Biz/Bild/Builder.nix b/Biz/Bild/Builder.nix
index a5a31c7..342569b 100644
--- a/Biz/Bild/Builder.nix
+++ b/Biz/Bild/Builder.nix
@@ -22,9 +22,9 @@ let
     skip = ["_" ".direnv"];
     filter = file: type:
       if lib.lists.elem (builtins.baseNameOf file) skip then false
-      # TODO: this means any new directory will cause a rebuild. this bad.  i
+      # TODO: this means any new directory will cause a rebuild. this bad. i
       # should recurse into the directory and match against the srcs. for now I
-      # just use postUnpack to delete empty dirs
+      # just use preBuild to delete empty dirs
       else if type == "directory" then true
       else if type == "regular" then lib.trivial.pipe file
         [ (f: lib.strings.removePrefix "${root}/" f)
@@ -32,8 +32,8 @@ let
         ]
       else false;
 
-    # clean up empty dirs
-    #postUnpack = "find $src -type d -empty -delete";
+    # remove empty directories, leftover from the src filter
+    preBuild = "find . -type d -empty -delete";
 
     src = lib.sources.cleanSourceWith {inherit filter; src = lib.sources.cleanSource root;};
 
@@ -41,26 +41,28 @@ let
       if isEmpty target.langdeps then
         []
       else
-      lib.attrsets.attrVals
+        lib.attrsets.attrVals
           target.langdeps
           (lib.attrsets.getAttrFromPath (lib.strings.splitString "." target.packageSet) bild);
+
     sysdeps_ =
       if isEmpty target.sysdeps then
         []
       else
         lib.attrsets.attrVals target.sysdeps pkgs;
+
     BIZ_ROOT = ".";
 
     builders = {
       base = stdenv.mkDerivation rec {
-        inherit name src BIZ_ROOT;
+        inherit name src BIZ_ROOT preBuild;
         buildInputs = langdeps_ ++ sysdeps_;
         installPhase = "install -D ${name} $out/bin/${name}";
         buildPhase = compileLine;
       };
 
       haskell = stdenv.mkDerivation rec {
-        inherit name src BIZ_ROOT;
+        inherit name src BIZ_ROOT preBuild;
         buildInputs = sysdeps_ ++ [
           (bild.haskell.ghcWith (p:
             (lib.attrsets.attrVals target.langdeps p)
@@ -71,7 +73,7 @@ let
       };
 
       c = stdenv.mkDerivation rec {
-        inherit name src BIZ_ROOT;
+        inherit name src BIZ_ROOT preBuild;
         buildInputs = langdeps_ ++ sysdeps_;
         installPhase = "install -D ${name} $out/bin/${name}";
         buildPhase = lib.strings.concatStringsSep " " [
@@ -98,7 +100,9 @@ let
           check python -m ${mainModule} test
         '';
         preBuild = ''
-          # initialize possibly-empty subdirectories as python modules
+          # remove empty directories, leftover from the src filter
+          find . -type d -empty -delete
+          # initialize remaining dirs as python modules
           find . -type d -exec touch {}/__init__.py \;
           # generate a minimal setup.py
           cat > setup.py << EOF
@@ -120,7 +124,7 @@ let
       };
     };
   in builders.${target.builder};
-# the caller gives us the Analysis type, which is a hashmap, but i need to
+# the bild caller gives us the Analysis type, which is a hashmap, but i need to
 # return a single drv, so just take the first one for now. ideally i would only
 # pass Target, one at a time, (perhaps parallelized in haskell land) and then i
 # wouldn't need all of this let nesting
diff --git a/Biz/Bild/Example.py b/Biz/Bild/Example.py
index 25686fa..5d165d8 100644
--- a/Biz/Bild/Example.py
+++ b/Biz/Bild/Example.py
@@ -1,6 +1,6 @@
 """
 Example Python file that also serves as a test case for bild.
-fernet."""
+"""
 # : out example
 # : dep cryptography
 import sys