From 671f860a1912ba45fa489354f84ec82a6f11ae96 Mon Sep 17 00:00:00 2001
From: Benoit Gagnon <benoit.gagnon@ubisoft.com>
Date: Wed, 24 Jul 2019 22:52:06 -0400
Subject: [PATCH] Shallow fetch for Git packages

If the server supports it, fetch a specific
revision with --depth 1. Otherwise, fall back
to the normal fetch.

This replaces the previous "clone" operation. The bandwidth and time savings
can be significant depending on the history
of the repository (number of commits).
---
 pkg/git.go | 38 +++++++++++++++++++++++++++++++++++---
 1 file changed, 35 insertions(+), 3 deletions(-)

diff --git a/pkg/git.go b/pkg/git.go
index d199ff9..2f53860 100644
--- a/pkg/git.go
+++ b/pkg/git.go
@@ -37,15 +37,47 @@ func NewGitPackage(source *spec.GitSource) Interface {
 }
 
 func (p *GitPackage) Install(ctx context.Context, dir, version string) (lockVersion string, err error) {
-	cmd := exec.CommandContext(ctx, "git", "clone", "-n", p.Source.Remote, dir)
+	cmd := exec.CommandContext(ctx, "git", "init")
 	cmd.Stdin = os.Stdin
 	cmd.Stdout = os.Stdout
 	cmd.Stderr = os.Stderr
+	cmd.Dir = dir
 	err = cmd.Run()
 	if err != nil {
 		return "", err
 	}
 
+	cmd = exec.CommandContext(ctx, "git", "remote", "add", "origin", p.Source.Remote)
+	cmd.Stdin = os.Stdin
+	cmd.Stdout = os.Stdout
+	cmd.Stderr = os.Stderr
+	cmd.Dir = dir
+	err = cmd.Run()
+	if err != nil {
+		return "", err
+	}
+
+	// Attempt shallow fetch at specific revision
+	cmd = exec.CommandContext(ctx, "git", "fetch", "--depth", "1", "origin", version)
+	cmd.Stdin = os.Stdin
+	cmd.Stdout = os.Stdout
+	cmd.Stderr = os.Stderr
+	cmd.Dir = dir
+	err = cmd.Run()
+	if err != nil {
+		// Fall back to normal fetch (all revisions)
+		cmd = exec.CommandContext(ctx, "git", "fetch", "origin")
+		cmd.Stdin = os.Stdin
+		cmd.Stdout = os.Stdout
+		cmd.Stderr = os.Stderr
+		cmd.Dir = dir
+		err = cmd.Run()
+		if err != nil {
+			return "", err
+		}
+	}
+
+	// If a Subdir is specificied, a sparsecheckout is sufficient
 	if p.Source.Subdir != "" {
 		cmd = exec.CommandContext(ctx, "git", "config", "core.sparsecheckout", "true")
 		cmd.Stdin = os.Stdin
@@ -55,9 +87,9 @@ func (p *GitPackage) Install(ctx context.Context, dir, version string) (lockVers
 		err = cmd.Run()
 		if err != nil {
 			return "", err
-		}	
+		}
 		glob := []byte(p.Source.Subdir + "/*\n")
-		ioutil.WriteFile(dir + "/.git/info/sparse-checkout", glob, 0644)
+		ioutil.WriteFile(dir+"/.git/info/sparse-checkout", glob, 0644)
 	}
 
 	cmd = exec.CommandContext(ctx, "git", "-c", "advice.detachedHead=false", "checkout", version)