fix: Revert to old SSH config section management in config-ssh (#2341)

cli/configssh_old.go

@@ -0,0 +1,66 @@
+package cli
+
+import (
+	"bytes"
+	"os"
+	"path/filepath"
+	"regexp"
+	"strings"
+)
+
+// This file contains config-ssh definitions that are deprecated, they
+// will be removed after a migratory period.
+
+const (
+	sshDefaultCoderConfigFileName = "~/.ssh/coder"
+	sshCoderConfigHeader          = "# This file is managed by coder. DO NOT EDIT."
+)
+
+// Regular expressions are used because SSH configs do not have
+// meaningful indentation and keywords are case-insensitive.
+var (
+	// Find the semantically correct include statement. Since the user can
+	// modify their configuration as they see fit, there could be:
+	// - Leading indentation (space, tab)
+	// - Trailing indentation (space, tab)
+	// - Select newline after Include statement for cleaner removal
+	// In the following cases, we will not recognize the Include statement
+	// and leave as-is (i.e. they're not supported):
+	// - User adds another file to the Include statement
+	// - User adds a comment on the same line as the Include statement
+	sshCoderIncludedRe = regexp.MustCompile(`(?m)^[\t ]*((?i)Include) coder[\t ]*[\r]?[\n]?$`)
+)
+
+// removeDeprecatedSSHIncludeStatement checks for the Include coder statement
+// and returns modified = true if it was removed.
+func removeDeprecatedSSHIncludeStatement(data []byte) (modifiedData []byte, modified bool) {
+	coderInclude := sshCoderIncludedRe.FindIndex(data)
+	if coderInclude == nil {
+		return data, false
+	}
+
+	// Remove Include statement.
+	d := append([]byte{}, data[:coderInclude[0]]...)
+	d = append(d, data[coderInclude[1]:]...)
+	data = d
+
+	return data, true
+}
+
+// readDeprecatedCoderConfigFile reads the deprecated split config file.
+func readDeprecatedCoderConfigFile(homedir, coderConfigFile string) (name string, data []byte, ok bool) {
+	if strings.HasPrefix(coderConfigFile, "~/") {
+		coderConfigFile = filepath.Join(homedir, coderConfigFile[2:])
+	}
+
+	b, err := os.ReadFile(coderConfigFile)
+	if err != nil {
+		return coderConfigFile, nil, false
+	}
+	if len(b) > 0 {
+		if !bytes.HasPrefix(b, []byte(sshCoderConfigHeader)) {
+			return coderConfigFile, nil, false
+		}
+	}
+	return coderConfigFile, b, true
+}