Allow overriding the build suffix

Prior to this commit, the build suffix (displayed to users at startup)
was always the top of tree git short hash. This is nice but it falls
down if someone is pulling a release from a tarball, zip file, or other
archive that does not include the .git folder or if the builder does not
have git installed.

As of this commit, the project will now build even in those cases
(displaying a "0" suffix). This change also allows the builder to
specify the suffix for packaging or other purposes via the "suffix"
property. E.g. `./gradlew build -P suffix="build35"`

I have no immediate plans to change my use of the git hash in releases
on GitHub, but hopefully this allows others additional flexibility.

Fixes #82

build.gradle.kts

@@ -71,10 +71,11 @@ tasks {
     }
 
     processResources {
+        inputs.property("suffix", project.findProperty("suffix") ?: "") // track suffix value as input
         expand(
             "projectName" to rootProject.name,
             "projectVersion" to version,
-            "projectGitHash" to getGitHash(),
+            "projectSuffix" to getSuffix(),
             "projectSourceRepo" to "https://github.com/zachbr/Dis4IRC"
         )
     }
@@ -94,11 +95,21 @@ license {
     }
 }
 
-fun getGitHash(): String {
-    val stdout = ByteArrayOutputStream() // cannot be fully qualified, ¯\_(ツ)_/¯
-    exec {
-        commandLine = listOf("git", "rev-parse", "--short", "HEAD")
-        standardOutput = stdout
+fun getSuffix(): String {
+    // If suffix was specified at build-time, use that.
+    // ./gradlew build -P suffix="suffixValue15"
+    project.findProperty("suffix")?.toString()?.let { return it }
+
+    // Fall back to git hash if suffix not set
+    return ByteArrayOutputStream().let { stdout ->
+        runCatching {
+            exec {
+                commandLine("git", "rev-parse", "--short", "HEAD")
+                standardOutput = stdout
+                errorOutput = ByteArrayOutputStream()
+                isIgnoreExitValue = true
+            }
+            stdout.toString().trim().takeIf { it.isNotEmpty() }
+        }.getOrNull() ?: "0"  // fall back to 0 if git falls through
     }
-    return stdout.toString().trim()
 }

src/main/kotlin/io/zachbr/dis4irc/Dis4IRC.kt

@@ -46,7 +46,7 @@ class Dis4IRC(args: Array<String>) {
     init {
         parseArguments(args)
 
-        logger.info("Dis4IRC v${Versioning.version}-${Versioning.gitHash}")
+        logger.info("Dis4IRC v${Versioning.version}-${Versioning.suffix}")
         logger.info("Source available at ${Versioning.sourceRepo}")
         logger.info("Available under the MIT License")
 
@@ -190,7 +190,7 @@ class Dis4IRC(args: Array<String>) {
 
     private fun printVersionInfo(minimal: Boolean = false) {
         // can't use logger, this has to be bare bones without prefixes or timestamps
-        println("Dis4IRC v${Versioning.version}-${Versioning.gitHash}")
+        println("Dis4IRC v${Versioning.version}-${Versioning.suffix}")
         if (minimal) {
             return
         }

src/main/kotlin/io/zachbr/dis4irc/util/Versioning.kt

@@ -22,9 +22,9 @@ object Versioning {
     val version: String
 
     /**
-     * Gets the top of tree git hash this version was built against
+     * Gets the build suffix, this may be the git hash or a value specified at build time
      */
-    val gitHash: String
+    val suffix: String
 
     /**
      * Gets the source repo of this project
@@ -34,7 +34,7 @@ object Versioning {
     init {
         val resources = this.javaClass.classLoader.getResources(JAR_PATH_TO_VERSIONING_INFO)
         var verOut = "Unknown version"
-        var gitHashOut = "Unknown Git Commit"
+        var suffixOut = "Unknown suffix"
         var repoOut = "Unknown source repo"
 
         if (resources.hasMoreElements()) {
@@ -45,14 +45,14 @@ object Versioning {
                     }
 
                     verOut = getValue("Version")
-                    gitHashOut = getValue("Git-Hash")
+                    suffixOut = getValue("Suffix")
                     repoOut = getValue("Source-Repo")
                 }
             }
         }
 
         version = verOut
-        gitHash = gitHashOut
+        suffix = suffixOut
         sourceRepo = repoOut
     }
 }

src/main/resources/dis4irc-versioning.txt

@@ -1,4 +1,4 @@
 Name: ${projectName}
 Version: ${projectVersion}
-Git-Hash: ${projectGitHash}
+Suffix: ${projectSuffix}
 Source-Repo: ${projectSourceRepo}