Add custom pager handling (#299)

* add custom pager handling

* ignore linter temporarily

* change condition

* add debug line

* add debug log

* add pager infos to README

* Update README.md

Co-authored-by: João Palet <joao.palet@outlook.com>

* edit README.md

* edit README.md

* Update README.md

Co-authored-by: Vicente Pinto <vicente.pinto@freiheit.com>

* Update README.md

Co-authored-by: Vicente Pinto <vicente.pinto@freiheit.com>

---------

Co-authored-by: João Palet <joao.palet@outlook.com>
Co-authored-by: Vicente Pinto <vicente.pinto@freiheit.com>

Author: 3 people

README.md

@@ -130,6 +130,33 @@ stackit config list
 
 You can also edit the configuration file manually.
 
+## Customization
+
+### Pager
+
+To specify a custom pager, use the `PAGER` environment variable.
+
+If the variable is not set, STACKIT CLI uses the `less` as default pager.
+
+When using `less` as a pager, STACKIT CLI will automatically pass following options
+- -F, --quit-if-one-screen - Less will automatically exit if the entire file can be displayed on the first screen.
+- -S, --chop-long-lines - Lines longer than the screen width will be chopped rather than being folded.
+- -w, --hilite-unread - Temporarily highlights the first "new" line after a forward movement of a full page.
+- -R, --RAW-CONTROL-CHARS - ANSI color and style sequences will be interpreted.
+
+> These options will not be added automatically if a custom pager is defined.
+> 
+> In that case, users can define the parameters by using the specific environment variable required by the `PAGER` (if supported).
+
+> 
+> For example, if user sets the `PAGER` environment variable to `less` and would like to pass some arguments, `LESS` environment variable must be used as following:
+
+> 
+> export PAGER="less"
+> 
+> export LESS="-R"
+
+
 ## Autocompletion
 
 If you wish to set up command autocompletion in your shell for the STACKIT CLI, please refer to our [autocompletion guide](./AUTOCOMPLETION.md).

internal/pkg/print/print.go

@@ -180,9 +180,15 @@ func (p *Printer) PagerDisplay(content string) error {
 	// -R: interprets ANSI color and style sequences
 	pagerCmd := exec.Command("less", "-F", "-S", "-w", "-R")
 
+	pager, pagerExists := os.LookupEnv("PAGER")
+	if pagerExists && pager != "nil" && pager != "" {
+		pagerCmd = exec.Command(pager) // #nosec G204
+	}
+
 	pagerCmd.Stdin = strings.NewReader(content)
 	pagerCmd.Stdout = p.Cmd.OutOrStdout()
 
+	p.Debug(DebugLevel, "using pager: %s", pagerCmd.Args[0])
 	err := pagerCmd.Run()
 	if err != nil {
 		p.Debug(ErrorLevel, "run pager command: %v", err)