include default ssh socket when given an ssh-based git url

Signed-off-by: Alex Couture-Beil <alex@earthly.dev>

bake/bake.go

@@ -534,7 +534,11 @@ func toBuildOpt(t *Target, inp *Input) (*build.Options, error) {
 	}
 	bo.Session = append(bo.Session, secrets)
 
-	ssh, err := build.ParseSSHSpecs(t.SSH)
+	sshSpecs := t.SSH
+	if len(sshSpecs) == 0 && build.IsGitSSH(contextPath) {
+		sshSpecs = []string{"default"}
+	}
+	ssh, err := build.ParseSSHSpecs(sshSpecs)
 	if err != nil {
 		return nil, err
 	}

build/ssh.go

@@ -5,6 +5,7 @@ import (
 
 	"github.com/moby/buildkit/session"
 	"github.com/moby/buildkit/session/sshforward/sshprovider"
+	"github.com/moby/buildkit/util/gitutil"
 )
 
 func ParseSSHSpecs(sl []string) (session.Attachable, error) {
@@ -29,3 +30,9 @@ func parseSSH(value string) (*sshprovider.AgentConfig, error) {
 	}
 	return &cfg, nil
 }
+
+// IsGitSSH returns true if the given repo URL is accessed over ssh
+func IsGitSSH(url string) bool {
+	_, gitProtocol := gitutil.ParseProtocol(url)
+	return gitProtocol == gitutil.SSHProtocol
+}

commands/build.go

@@ -124,7 +124,11 @@ func runBuild(dockerCli command.Cli, in buildOptions) error {
 	}
 	opts.Session = append(opts.Session, secrets)
 
-	ssh, err := build.ParseSSHSpecs(in.ssh)
+	sshSpecs := in.ssh
+	if len(sshSpecs) == 0 && build.IsGitSSH(in.contextPath) {
+		sshSpecs = []string{"default"}
+	}
+	ssh, err := build.ParseSSHSpecs(sshSpecs)
 	if err != nil {
 		return err
 	}