refactor(commands): separate commands and its core into two folders (#32)

- I think it would be better if one for commands only, one for the spec
handling core logic so people won't be confused by the core logic inside
the commands folder (cleaner I guess)
- Regen docs

spec/utils.go

@@ -0,0 +1,68 @@
+package spec
+
+import (
+	"strings"
+)
+
+// SplitAliasTokens parses the input string into shell-like tokens handling quotes
+// example: SplitAliasTokens("git commit -m \"hello world\"")
+func Tokenize(s string) []string {
+	tokens := []string{}
+	var current strings.Builder
+	inQuote := false
+	var quoteChar rune
+
+	escaped := false
+	for _, c := range s {
+		if escaped {
+			current.WriteRune(c)
+			escaped = false
+			continue
+		}
+
+		switch {
+		case c == '\\':
+			escaped = true
+		case !inQuote && (c == '"' || c == '\''):
+			inQuote = true
+			quoteChar = c
+		case inQuote && c == quoteChar:
+			inQuote = false
+		case c == ' ' && !inQuote:
+			if current.Len() > 0 {
+				tokens = append(tokens, current.String())
+				current.Reset()
+			}
+		default:
+			current.WriteRune(c)
+		}
+	}
+
+	tokens = append(tokens, current.String())
+	return tokens
+}
+
+// HasPrefix checks if s starts with prefix using case-insensitive matching
+func HasPrefix(s, prefix string) bool {
+	if len(prefix) > len(s) {
+		return false
+	}
+	for i := 0; i < len(prefix); i++ {
+		a, b := s[i], prefix[i]
+		if a >= 'A' && a <= 'Z' {
+			a += 32
+		}
+		if b >= 'A' && b <= 'Z' {
+			b += 32
+		}
+		if a != b {
+			return false
+		}
+	}
+	return true
+}
+
+// CI = case insensitive
+func HasPrefixCI(s, prefix string) bool {
+	return HasPrefix(s, prefix)
+}