markdown: dont emit ansi sequences when not emitting to tty (#491)

Allows generating a plain text version of an issue (i.e. without colors and other terminal formatting) when storing stdout in a file.
```
tea issue --comments 1 > issue1.txt
```

`IsInteractive()` had to be moved to avoid a recursive import chain.

---

In the future, it would be nice to also respect the `--output` flag. This flag is currently designed for tabular output, but we could add more supported values like `markdown` `ansi`, `plain` to it

Co-authored-by: Norwin <git@nroo.de>
Co-authored-by: 6543 <6543@obermui.de>
Reviewed-on: https://gitea.com/gitea/tea/pulls/491
Reviewed-by: 6543 <6543@obermui.de>
Reviewed-by: delvh <dev.lh@web.de>

modules/interact/comments.go

@@ -27,7 +27,7 @@ func ShowCommentsMaybeInteractive(ctx *context.TeaContext, idx int64, totalComme
 			return err
 		}
 		print.Comments(comments)
-	} else if IsInteractive() && !ctx.IsSet("comments") {
+	} else if print.IsInteractive() && !ctx.IsSet("comments") {
 		// if we're interactive, but --comments hasn't been explicitly set to false
 		if err := ShowCommentsPaginated(ctx, idx, totalComments); err != nil {
 			fmt.Printf("error while loading comments: %v\n", err)
@@ -70,11 +70,6 @@ func ShowCommentsPaginated(ctx *context.TeaContext, idx int64, totalComments int
 	return nil
 }
 
-// IsInteractive checks if the output is piped, but NOT if the session is run interactively..
-func IsInteractive() bool {
-	return terminal.IsTerminal(int(os.Stdout.Fd()))
-}
-
 // IsStdinPiped checks if stdin is piped
 func IsStdinPiped() bool {
 	return !terminal.IsTerminal(int(os.Stdin.Fd()))

modules/print/formatters.go

@@ -6,13 +6,20 @@ package print
 
 import (
 	"fmt"
+	"os"
 	"regexp"
 	"time"
 
 	"code.gitea.io/sdk/gitea"
 	"github.com/muesli/termenv"
+	"golang.org/x/crypto/ssh/terminal"
 )
 
+// IsInteractive checks if the output is piped, but NOT if the session is run interactively..
+func IsInteractive() bool {
+	return terminal.IsTerminal(int(os.Stdout.Fd()))
+}
+
 // captures the repo URL part <host>/<owner>/<repo> of an url
 var repoURLRegex = regexp.MustCompile("^([[:alnum:]]+://[^/]+(?:/[[:alnum:]]+){2})/.*")
 

modules/print/markdown.go

@@ -16,8 +16,15 @@ import (
 // If the input could not be parsed, it is printed unformatted, the error
 // is returned anyway.
 func outputMarkdown(markdown string, baseURL string) error {
+	var styleOption glamour.TermRendererOption
+	if IsInteractive() {
+		styleOption = glamour.WithAutoStyle()
+	} else {
+		styleOption = glamour.WithStandardStyle("notty")
+	}
+
 	renderer, err := glamour.NewTermRenderer(
-		glamour.WithAutoStyle(),
+		styleOption,
 		glamour.WithBaseURL(baseURL),
 		glamour.WithPreservedNewLines(),
 		glamour.WithWordWrap(getWordWrap()),