Automatically generate the version based on the git tag

.gitignore

@@ -10,4 +10,5 @@ dvm/dvm/dvm
 bin/dvm
 *.deps
 .dub
-bin/*
+bin/*
+tmp

dub.json

@@ -12,7 +12,7 @@
     "targetPath": "bin",
     "sourcePaths": ["dvm"],
     "importPaths": ["dvm"],
-    "stringImportPaths": ["resources"],
+    "stringImportPaths": ["resources", "tmp"],
 
     "excludedSourceFiles-posix": [
         "dvm/util/DvmRegistry.d",
@@ -25,5 +25,13 @@
 
     "dependencies": {
         "mambo": "~>0.0.9"
-    }
+    },
+
+    "preGenerateCommands-posix": [
+      "$$DC -run $PACKAGE_DIR/tools/generate_version.d"
+    ],
+
+    "preGenerateCommands-windows": [
+      "%DC% -run $PACKAGE_DIR/tools/generate_version.d"
+    ]
 }

dvm/dvm/Version.d

@@ -6,4 +6,7 @@
  */
 module dvm.dvm.Version;
 
-enum Version = "0.4.5";
+import std.range : drop;
+import std.string : strip;
+
+enum Version = import("version").strip.drop(1);

tools/generate_version.d

@@ -0,0 +1,36 @@
+import std.file : exists, mkdirRecurse, readText, write;
+import std.path : buildPath;
+import std.process : execute, env = environment;
+import std.string : strip;
+
+enum outputDirectory = "tmp";
+enum versionFile = "version";
+
+void main()
+{
+    const outputDirectory = env.get("DUB_PACKAGE_DIR", ".").buildPath("tmp");
+
+    mkdirRecurse(outputDirectory);
+
+    outputDirectory
+        .buildPath("version")
+        .updateIfChanged(generateVersion);
+}
+
+string generateVersion()
+{
+    const result = execute(["git", "describe", "--dirty", "--tags", "--always"]);
+
+    if (result.status != 0)
+        throw new Exception("Failed to execute 'git describe'");
+
+    return result.output.strip;
+}
+
+void updateIfChanged(const string path, const string content)
+{
+    const existingContent = path.exists ? path.readText : "";
+
+    if (content != existingContent)
+        write(path, content);
+}