Issue #704: Use built in git-describe (#705)

Use built in git-describe

Author: esword

changelog/@unreleased/pr-705.v2.yml

@@ -0,0 +1,7 @@
+type: break
+break:
+  description: Use built in git-describe rather than an expensive recreation of it
+    to support older versions of git. This version requires git version >=1.8.4 (released
+    23rd August 2013).
+  links:
+  - https://github.com/palantir/gradle-git-version/pull/705

src/main/java/com/palantir/gradle/gitversion/Git.java

@@ -17,8 +17,6 @@
 package com.palantir.gradle.gitversion;
 
 import com.google.common.annotations.VisibleForTesting;
-import com.google.common.base.Preconditions;
-import com.google.common.base.Splitter;
 import java.io.BufferedReader;
 import java.io.File;
 import java.io.IOException;
@@ -27,23 +25,14 @@
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.HashMap;
-import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
-import java.util.Set;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
-/**
- * Mimics git describe by using rev-list to support versions of git < 1.8.4.
- */
 class Git {
     private static final Logger log = LoggerFactory.getLogger(Git.class);
 
-    private static final Splitter LINE_SPLITTER =
-            Splitter.on(System.getProperty("line.separator")).omitEmptyStrings();
-    private static final Splitter WORD_SPLITTER = Splitter.on(" ").omitEmptyStrings();
-
     private final File directory;
 
     Git(File directory) {
@@ -166,29 +155,18 @@ public Boolean isClean() {
 
     public String describe(String prefix) {
         try {
-            // Get SHAs of all tags, we only need to search for these later on
-            Set<String> tagRefs = new HashSet<>();
-            for (String tag : LINE_SPLITTER.splitToList(runGitCmd("show-ref", "--tags", "-d"))) {
-                List<String> parts = WORD_SPLITTER.splitToList(tag);
-                Preconditions.checkArgument(parts.size() == 2, "Could not parse output of `git show-ref`: %s", parts);
-                tagRefs.add(parts.get(0));
-            }
-
-            List<String> revs = LINE_SPLITTER.splitToList(runGitCmd("rev-list", "--first-parent", "HEAD"));
-            for (int depth = 0; depth < revs.size(); depth++) {
-                String rev = revs.get(depth);
-                if (tagRefs.contains(rev)) {
-                    String exactTag = runGitCmd("describe", "--tags", "--exact-match", "--match=" + prefix + "*", rev);
-                    if (!exactTag.isEmpty()) {
-                        return depth == 0
-                                ? exactTag
-                                : String.format("%s-%s-g%s", exactTag, depth, GitUtils.abbrevHash(revs.get(0)));
-                    }
-                }
+            String result = runGitCmd(
+                    "describe",
+                    "--tags",
+                    "--always",
+                    "--first-parent",
+                    "--abbrev=7",
+                    "--match=" + prefix + "*",
+                    "HEAD");
+            if (result.isEmpty()) {
+                return null;
             }
-
-            // No tags found, so return commit hash of HEAD
-            return GitUtils.abbrevHash(runGitCmd("rev-parse", "HEAD"));
+            return result;
         } catch (IOException | InterruptedException | RuntimeException e) {
             log.debug("Native git describe failed", e);
             return null;

src/main/java/com/palantir/gradle/gitversion/GitUtils.java

@@ -54,19 +54,12 @@ private boolean isClean() {
     }
 
     private String description() {
-        String rawDescription = expensiveComputeRawDescription();
+        String rawDescription = nativeGitInvoker.describe(args.getPrefix());
         String processedDescription =
                 rawDescription == null ? null : rawDescription.replaceFirst("^" + args.getPrefix(), "");
         return processedDescription;
     }
 
-    private String expensiveComputeRawDescription() {
-
-        String nativeGitDescribe = nativeGitInvoker.describe(args.getPrefix());
-
-        return nativeGitDescribe;
-    }
-
     @Override
     public boolean getIsCleanTag() {
         return isClean() && descriptionIsPlainTag();