GitUtils: Extract lines matching a pattern from a set of commits

In preparation of SOLMAN features. Here we need to get a change
document ID out of the commit message.

Start and end commit can be provided as well as a log format
and a filter condition.

src/com/sap/piper/GitUtils.groovy

@@ -15,3 +15,17 @@ String getGitCommitIdOrNull() {
 String getGitCommitId() {
     return sh(returnStdout: true, script: 'git rev-parse HEAD').trim()
 }
+
+String[] extractLogLines(String filter = '',
+                         String from = 'origin/master',
+                         String to = 'HEAD',
+                         String format = '%b') {
+
+    sh ( returnStdout: true,
+         script: """#!/bin/bash
+                    git log --pretty=format:${format} ${from}..${to}
+                 """
+       )?.split('\n')
+        ?.findAll { line -> line ==~ /${filter}/ }
+
+}

test/groovy/com/sap/piper/GitUtilsTest.groovy

@@ -10,9 +10,14 @@ import util.JenkinsShellCallRule
 import util.Rules
 
 import static org.junit.Assert.assertEquals
-import static org.junit.Assert.assertFalse
+import static org.hamcrest.Matchers.equalTo
 import static org.junit.Assert.assertTrue
+import static org.junit.Assert.assertFalse
+import static org.hamcrest.Matchers.is
+import static org.hamcrest.Matchers.notNullValue
+import static org.junit.Assert.assertNotNull
 import static org.junit.Assert.assertNull
+import static org.junit.Assert.assertThat
 
 class GitUtilsTest extends BasePiperTest {
 
@@ -52,4 +57,38 @@ class GitUtilsTest extends BasePiperTest {
         assertNull(gitUtils.getGitCommitIdOrNull())
     }
 
+    @Test
+    void testExtractLogLinesWithDefaults() {
+        gitUtils.extractLogLines()
+        assertTrue(jscr.shell
+                         .stream()
+                           .anyMatch( { it ->
+                             it.contains('git log --pretty=format:%b origin/master..HEAD')}))
+    }
+
+    @Test
+    void testExtractLogLinesWithCustomValues() {
+        gitUtils.extractLogLines('myFilter', 'HEAD~5', 'HEAD~1', '%B')
+        assertTrue( jscr.shell
+                          .stream()
+                            .anyMatch( { it ->
+                               it.contains('git log --pretty=format:%B HEAD~5..HEAD~1')}))
+    }
+
+    @Test
+    void testExtractLogLinesFilter() {
+        jscr.setReturnValue('#!/bin/bash git log --pretty=format:%b origin/master..HEAD', 'abc\n123')
+        String[] log = gitUtils.extractLogLines('12.*')
+        assertThat(log, is(notNullValue()))
+        assertThat(log.size(),is(equalTo(1)))
+        assertThat(log[0], is(equalTo('123')))
+    }
+
+    @Test
+    void testExtractLogLinesFilterNoMatch() {
+        jscr.setReturnValue('#!/bin/bash git log --pretty=format:%b origin/master..HEAD', 'abc\n123')
+        String[] log = gitUtils.extractLogLines('xyz')
+        assertNotNull(log)
+        assertThat(log.size(),is(equalTo(0)))
+	}
 }