Add download-git target to Makefile

The new 'download-git' target can be used like this:

$ make GIT_REV=test-next download-git

to download a tarball from:

https://gitlab.com/gitlab-org/gitlab-git/-/jobs/artifacts/test-next/raw/git_full_bins.tgz?job=build

3 files changed, 88 insertions, 0 deletions

diff --git a/Makefile b/Makefile
index 12fb7bf22..069a30535 100644
--- a/Makefile
+++ b/Makefile
@@ -116,6 +116,14 @@ no-changes: prepare-build
 smoke-test: prepare-build
 	cd $(BUILD_DIR) && $(MAKE) $@
 
+.PHONY: download-git
+download-git: prepare-build
+	cd $(BUILD_DIR) && $(MAKE) $@
+
+.PHONY: build-git
+build-git: prepare-build
+	cd $(BUILD_DIR) && $(MAKE) $@
+
 .PHONY: prepare-build
 prepare-build: $(BUILD_DIR)/.ok update-makefile
 $(BUILD_DIR)/.ok:
diff --git a/_support/Makefile.template b/_support/Makefile.template
index feae6dcce..672331bc7 100644
--- a/_support/Makefile.template
+++ b/_support/Makefile.template
@@ -285,3 +285,21 @@ no-changes:
 
 smoke-test: all rspec
 	@cd {{ .SourceDir }} && go test ./internal/rubyserver
+
+.PHONY: download-git
+download-git:
+	@echo "Getting Git from {{ .GitArtifactUrl }}"
+	wget -P {{ .BuildDir }} -O {{ .GitBuildTarball }} {{ .GitArtifactUrl }}
+	rm -rf {{ .GitInstallDir }}
+	mkdir -p {{ .GitInstallDir }}
+	tar -C {{ .GitInstallDir }} -xvzf {{ .BuildDir }}/{{ .GitBuildTarball }}
+
+.PHONY: build-git
+build-git:
+	@echo "Getting Git from {{ .GitDefaultRepoUrl }}"
+	rm -rf {{ .GitSourceDir }} {{ .GitInstallDir }}
+	git clone {{ .GitDefaultRepoUrl }} {{ .GitSourceDir }}
+	git -C {{ .GitSourceDir }} checkout {{ .GitDefaultRev }}
+	rm -rf {{ .GitInstallDir }}
+	mkdir -p {{ .GitInstallDir }}
+	$(MAKE) -C {{ .GitSourceDir }} prefix={{ .GitDefaultPrefix }} {{ .GitBuildOptions }} install
diff --git a/_support/makegen.go b/_support/makegen.go
index 57b6e39dc..a821d0da7 100644
--- a/_support/makegen.go
+++ b/_support/makegen.go
@@ -326,6 +326,68 @@ func (gm *gitalyMake) IsGDK() bool {
 	return err == nil
 }
 
+// Variables used with Git
+
+func (gm *gitalyMake) GitDefaultRev() string {
+	rev := os.Getenv("GIT_REV")
+	if rev != "" {
+		return rev
+	}
+	return "master"
+}
+
+func (gm *gitalyMake) GitDefaultBuildJob() string {
+	job := os.Getenv("GIT_BUILD_JOB")
+	if job != "" {
+		return job
+	}
+	return "build"
+}
+
+func (gm *gitalyMake) GitInstallDir() string { return filepath.Join(gm.BuildDir(), "git") }
+func (gm *gitalyMake) GitBuildTarball() string { return "git_full_bins.tgz"}
+
+func (gm *gitalyMake) GitArtifactUrl() string {
+	return "https://gitlab.com/gitlab-org/gitlab-git/-/jobs/artifacts/" +
+		gm.GitDefaultRev() + "/raw/" +
+		gm.GitBuildTarball() + "?job=" +
+		gm.GitDefaultBuildJob()
+}
+
+func (gm *gitalyMake) GitDefaultRepoUrl() string {
+	url := os.Getenv("GIT_REPO_URL")
+	if url != "" {
+		return url
+	}
+	return "https://gitlab.com/gitlab-org/gitlab-git.git"
+}
+
+func (gm *gitalyMake) GitSourceDir() string { return filepath.Join(gm.BuildDir(), "src", "git") }
+
+func (gm *gitalyMake) GitBuildOptions() string {
+	buildOptions := []string{
+		"-j 8",			// use multiple parallele jobs
+		"DEVELOPER=1",		// activate developer checks
+		"CFLAGS='-O0 -g3'",	// make it easy to debug in case of crashes
+		"NO_PERL=YesPlease",
+		"NO_EXPAT=YesPlease",
+		"NO_TCLTK=YesPlease",
+		"NO_GETTEXT=YesPlease",
+		"NO_PYTHON=YesPlease",
+		"NO_INSTALL_HARDLINKS=YesPlease",
+		"NO_R_TO_GCC_LINKER=YesPlease",
+	}
+	return strings.Join(buildOptions, " ")
+}
+
+func (gm *gitalyMake) GitDefaultPrefix() string {
+	prefix := os.Getenv("GIT_PREFIX")
+	if prefix != "" {
+		return prefix
+	}
+	return gm.GitInstallDir()
+}
+
 var templateText = func() string {
 	contents, err := ioutil.ReadFile("../_support/Makefile.template")
 	if err != nil {