cat : --keep-header and --keep-title : decapitate by default

cat/cat.go

@@ -13,36 +13,71 @@ import (
 )
 
 const (
-	CMD       = cmd.Cat
-	SUMMARY   = "cat um files together using a filelist"
-	SEPARATOR = "\n---\n\n"
+	CMD            = cmd.Cat
+	SUMMARY        = "cat um files together using a filelist. removes header by default"
+	HR_BLOCK       = "\n---\n\n"
+	DOUBLE_NEWLINE = "\n\n"
+	H1             = "# "
 )
 
 type options struct {
-	Filelist flags.Arg
-	Base     flags.Flag[string]
-	Help     flags.Flag[bool]
+	Filelist   flags.Arg
+	Base       flags.Flag[string]
+	KeepHeader flags.Flag[bool]
+	KeepTitle  flags.Flag[bool]
+	Help       flags.Flag[bool]
 }
 
 func initOpts() options {
 	return options{
 		flags.Arg{"", "filelist. accepts from stdin if not provided"},
 		flags.Flag[string]{"--base", "-b", "", "base directory prepended to files in filelist"},
+		flags.Flag[bool]{"--keep-header", "-d", false, "preserve um headers in concatenated file. overrides --keep-title"},
+		flags.Flag[bool]{"--keep-title", "-t", false, "preserve um titles in concatenated file"},
 		flags.Flag[bool]{"--help", "-h", false, "show help"},
 	}
 }
 
-func cat(files []string, base string) (string, error) {
+// remove the um header:
+//
+// # title
+// : date
+// + tag
+//
+// optionally keep just the # title
+func decapitate(s string, opts options) string {
+	// if there's no header at all, forget it:
+	if opts.KeepHeader.IsSet() || !strings.HasPrefix(s, H1) {
+		return s
+	}
+	// I'd rather slice and dice than mess with regex
+	head, tail, ok := strings.Cut(s, DOUBLE_NEWLINE)
+	if !ok {
+		// head is complete if sep wasn't found:
+		return head
+	}
+	s = tail
+	if opts.KeepTitle.IsSet() {
+		// we just take the first line. but when the header consists only of the title, there is no newline:
+		if title, _, ok := strings.Cut(head, pipe.Newline); ok || !strings.Contains(head, pipe.Newline) {
+			s = fmt.Sprintf("%s%s%s", title, DOUBLE_NEWLINE, s)
+		}
+	}
+	return s
+}
+
+func cat(files []string, opts options) (string, error) {
 	ff := make([]string, 0, len(files))
 	for _, f := range files {
-		f := filepath.Join(base, f)
-		dat, err := os.ReadFile(f)
+		bf := filepath.Join(opts.Base.Val, f)
+		dat, err := os.ReadFile(bf)
 		if err != nil {
 			return "", fmt.Errorf("error opening target file: %w", err)
 		}
-		ff = append(ff, string(dat))
+		s := decapitate(string(dat), opts)
+		ff = append(ff, s)
 	}
-	return strings.Join(ff, SEPARATOR), nil
+	return strings.Join(ff, HR_BLOCK), nil
 }
 
 func Cat(args []string) {
@@ -52,7 +87,7 @@ func Cat(args []string) {
 	if err != nil {
 		log.Fatalf("um %s: %s", CMD, err)
 	}
-	s, err := cat(files, opts.Base.Val)
+	s, err := cat(files, opts)
 	if err != nil {
 		log.Fatalf("um %s: %s", CMD, err)
 	}