Fix empty output from git-plan command (#50)

Currently the git-plan command returns an empty output. This is due to a race
condition in the command runner where the output is not captured correctly
before the command stops.

The Go tool chain is also updated to support dependencies using new package
errors functions, e.g. errors.As.

Co-authored-by: Bjørn Sørensen <bso@lunar.app>

.travis.yml

@@ -1,7 +1,7 @@
 language: go
 
 go:
-- "1.11.x"
+- "1.15.x"
 
 script: |
   echo "Build shuttle" &&
@@ -17,4 +17,4 @@ deploy:
   script: curl -sL https://git.io/goreleaser | bash
   on:
     tags: true
-    condition: $TRAVIS_OS_NAME = linux
+    condition: $TRAVIS_OS_NAME = linux

go.mod

@@ -5,7 +5,7 @@ require (
 	github.com/Masterminds/sprig v2.16.0+incompatible
 	github.com/aokoli/goutils v1.0.1 // indirect
 	github.com/davecgh/go-spew v1.1.1 // indirect
-	github.com/go-cmd/cmd v1.0.3
+	github.com/go-cmd/cmd v1.2.0
 	github.com/go-test/deep v1.0.1 // indirect
 	github.com/google/uuid v1.0.0 // indirect
 	github.com/huandu/xstrings v1.2.0 // indirect

go.sum

@@ -8,6 +8,8 @@ github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/go-cmd/cmd v1.0.3 h1:N4lOnQy9gKNXLDnjoyRLLXG5sRqEzvFtdHjQysBez/g=
 github.com/go-cmd/cmd v1.0.3/go.mod h1:y8q8qlK5wQibcw63djSl/ntiHUHXHGdCkPk0j4QeW4s=
+github.com/go-cmd/cmd v1.2.0 h1:Aohz0ZG0nQbvT4z55Mh+fdegX48GSAXL3cSsbYxRfvI=
+github.com/go-cmd/cmd v1.2.0/go.mod h1:XgKkd0L6sv9WcYV0FS8RfG1RJCSTVHTsLeAD2pTgHt0=
 github.com/go-test/deep v1.0.1 h1:UQhStjbkDClarlmv0am7OXXO4/GaPdCGiUiMTvi28sg=
 github.com/go-test/deep v1.0.1/go.mod h1:wGDj63lr65AM2AQyKZd/NYHGb0R+1RLqB8NKt3aSFNA=
 github.com/google/uuid v1.0.0 h1:b4Gk+7WdP/d3HZH8EJsZpvV7EtDOgaZLtnaNGIu1adA=

pkg/git/main.go

@@ -134,22 +134,39 @@ func GetGitPlan(plan string, localShuttleDirectoryPath string, uii ui.UI, skipGi
 }
 
 func RunGitPlanCommand(command string, plan string, uii ui.UI) {
+
 	cmdOptions := go_cmd.Options{
+		Buffered:  false,
 		Streaming: true,
 	}
 	execCmd := go_cmd.NewCmdOptions(cmdOptions, "sh", "-c", "cd '"+plan+"'; git "+command)
 	execCmd.Env = os.Environ()
+
+	doneChan := make(chan struct{})
 	go func() {
-		for {
+		defer close(doneChan)
+
+		for execCmd.Stdout != nil || execCmd.Stderr != nil {
 			select {
-			case line := <-execCmd.Stdout:
+			case line, open := <-execCmd.Stdout:
+				if !open {
+					execCmd.Stdout = nil
+					continue
+				}
 				uii.Infoln("%s", line)
-			case line := <-execCmd.Stderr:
+			case line, open := <-execCmd.Stderr:
+				if !open {
+					execCmd.Stderr = nil
+					continue
+				}
 				uii.Infoln("%s", line)
 			}
 		}
 	}()
+
 	status := <-execCmd.Start()
+	<-doneChan
+
 	if status.Exit > 0 {
 		os.Exit(status.Exit)
 	}