From a9a62fe9761fa11a81f1f341efe7510151e712c4 Mon Sep 17 00:00:00 2001
From: Steve Streeting <steve@stevestreeting.com>
Date: Thu, 8 Oct 2015 17:40:38 +0100
Subject: [PATCH] Add utility functions for testing git version

---
 git/git.go      | 53 +++++++++++++++++++++++++++++++++++++++++++++++++
 git/git_test.go | 13 ++++++++++++
 2 files changed, 66 insertions(+)

diff --git a/git/git.go b/git/git.go
index c28160c0..5178a1eb 100644
--- a/git/git.go
+++ b/git/git.go
@@ -8,6 +8,7 @@ import (
 	"os"
 	"os/exec"
 	"regexp"
+	"strconv"
 	"strings"
 	"time"
 
@@ -183,6 +184,17 @@ func (c *gitConfig) Version() (string, error) {
 	return simpleExec("git", "version")
 }
 
+// IsVersionAtLeast returns whether the git version is the one specified or higher
+// argument is plain version string separated by '.' e.g. "2.3.1" but can omit minor/patch
+func (c *gitConfig) IsGitVersionAtLeast(ver string) bool {
+	gitver, err := c.Version()
+	if err != nil {
+		tracerx.Printf("Error getting git version: %v", err)
+		return false
+	}
+	return IsVersionAtLeast(gitver, ver)
+}
+
 // simpleExec is a small wrapper around os/exec.Command.
 func simpleExec(name string, args ...string) (string, error) {
 	tracerx.Printf("run_command: '%s' %s", name, strings.Join(args, " "))
@@ -340,3 +352,44 @@ func GetCommitSummary(commit string) (*CommitSummary, error) {
 	}
 
 }
+// IsVersionAtLeast compares 2 version strings (ok to be prefixed with 'git version', ignores)
+func IsVersionAtLeast(actualVersion, desiredVersion string) bool {
+	// Capture 1-3 version digits, optionally prefixed with 'git version' and possibly
+	// with suffixes which we'll ignore (e.g. unstable builds, MinGW versions)
+	verregex := regexp.MustCompile(`(?:git version\s+)?(\d+)(?:.(\d+))?(?:.(\d+))?.*`)
+
+	var atleast uint64
+	// Support up to 1000 in major/minor/patch digits
+	const majorscale = 1000 * 1000
+	const minorscale = 1000
+
+	if match := verregex.FindStringSubmatch(desiredVersion); match != nil {
+		// Ignore errors as regex won't match anything other than digits
+		major, _ := strconv.Atoi(match[1])
+		atleast += uint64(major * majorscale)
+		if len(match) > 2 {
+			minor, _ := strconv.Atoi(match[2])
+			atleast += uint64(minor * minorscale)
+		}
+		if len(match) > 3 {
+			patch, _ := strconv.Atoi(match[3])
+			atleast += uint64(patch)
+		}
+	}
+
+	var actual uint64
+	if match := verregex.FindStringSubmatch(actualVersion); match != nil {
+		major, _ := strconv.Atoi(match[1])
+		actual += uint64(major * majorscale)
+		if len(match) > 2 {
+			minor, _ := strconv.Atoi(match[2])
+			actual += uint64(minor * minorscale)
+		}
+		if len(match) > 3 {
+			patch, _ := strconv.Atoi(match[3])
+			actual += uint64(patch)
+		}
+	}
+
+	return actual >= atleast
+}
diff --git a/git/git_test.go b/git/git_test.go
index bbec2a67..55fb971a 100644
--- a/git/git_test.go
+++ b/git/git_test.go
@@ -184,3 +184,16 @@ func TestResolveEmptyCurrentRef(t *testing.T) {
 	_, err := CurrentRef()
 	assert.NotEqual(t, nil, err)
 }
+func TestVersionCompare(t *testing.T) {
+
+	assert.Equal(t, true, IsVersionAtLeast("2.6.0", "2.6.0"))
+	assert.Equal(t, true, IsVersionAtLeast("2.6.0", "2.6"))
+	assert.Equal(t, true, IsVersionAtLeast("2.6.0", "2"))
+	assert.Equal(t, true, IsVersionAtLeast("2.6.10", "2.6.5"))
+	assert.Equal(t, true, IsVersionAtLeast("2.8.1", "2.7.2"))
+
+	assert.Equal(t, false, IsVersionAtLeast("1.6.0", "2"))
+	assert.Equal(t, false, IsVersionAtLeast("2.5.0", "2.6"))
+	assert.Equal(t, false, IsVersionAtLeast("2.5.0", "2.5.1"))
+	assert.Equal(t, false, IsVersionAtLeast("2.5.2", "2.5.10"))
+}