feat: implement GNU-style command line options with pflag

- Add pflag dependency for POSIX/GNU-style command line parsing
- Replace Go standard flag package with pflag for better UX
- Implement long options with double dashes (--config, --max-messages, --help)
- Add short option aliases with single dashes (-c, -m, -h)
- Update help message with proper formatting and application description
- Update all documentation to reflect new flag syntax
- Update test scripts to use new command line format

GNU-style options provide better usability:
- Long descriptive options with --flag-name format
- Short single-character aliases for common options
- Standard help flag behavior with --help/-h
- Compatible with shell completion and standard conventions

Command line interface now supports:
- --config/-c FILE: Path to configuration file
- --max-messages/-m N: Message processing limit per mailbox
- --help/-h: Show help message and exit

All existing functionality preserved with improved command line experience.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

CLAUDE.md

@@ -20,13 +20,13 @@ cd go && go build -o mail2couch .
 cd go && ./mail2couch
 
 # Run with specific config file
-cd go && ./mail2couch -config /path/to/config.json
+cd go && ./mail2couch --config /path/to/config.json
 
 # Run with message limit (useful for large mailboxes)
-cd go && ./mail2couch -max-messages 100
+cd go && ./mail2couch --max-messages 100
 
 # Run with both config and message limit
-cd go && ./mail2couch -config /path/to/config.json -max-messages 50
+cd go && ./mail2couch --config /path/to/config.json --max-messages 50
 
 # Run linting/static analysis
 cd go && go vet ./...
@@ -80,7 +80,7 @@ The application uses `config.json` for configuration with the following structur
 ### Configuration File Discovery
 
 The application automatically searches for configuration files in the following order:
-1. Path specified by `-config` command line flag
+1. Path specified by `--config`/`-c` command line flag
 2. `./config.json` (current working directory)
 3. `./config/config.json` (config subdirectory)
 4. `~/.config/mail2couch/config.json` (user XDG config directory)
@@ -104,7 +104,7 @@ This design ensures the same `config.json` format will work for both Go and Rust
 - ✅ Sync vs Archive mode implementation
 - ✅ CouchDB attachment storage for email attachments
 - ✅ Full message body and attachment handling with MIME multipart support
-- ✅ Command line argument support (--max-messages flag)
+- ✅ Command line argument support (GNU-style --max-messages/-m and --config/-c flags)
 - ✅ Per-account CouchDB databases for better organization
 - ✅ Incremental sync functionality with IMAP SEARCH and sync metadata tracking
 - ❌ Rust implementation

README.md

@@ -39,7 +39,7 @@ A powerful email backup utility that synchronizes mail from IMAP accounts to Cou
 
 ### Operational Features
 - **Automatic Config Discovery**: Finds configuration files in standard locations
-- **Command Line Control**: Override settings with `--max-messages` and `--config` flags
+- **Command Line Control**: GNU-style options with `--max-messages`/`-m` and `--config`/`-c` flags
 - **Comprehensive Logging**: Detailed output for monitoring and troubleshooting
 - **Error Resilience**: Graceful handling of network issues and server problems
 
@@ -105,7 +105,7 @@ The application will:
 ### Configuration File Discovery
 
 mail2couch automatically searches for configuration files in this order:
-1. Path specified by `--config` flag
+1. Path specified by `--config`/`-c` flag
 2. `./config.json` (current directory)
 3. `./config/config.json` (config subdirectory)
 4. `~/.config/mail2couch/config.json` (user config directory)
@@ -117,8 +117,9 @@ mail2couch automatically searches for configuration files in this order:
 ./mail2couch [options]
 
 Options:
-  --config PATH        Specify configuration file path
-  --max-messages N     Limit messages processed per mailbox per run (0 = unlimited)
+  -c, --config FILE        Path to configuration file
+  -m, --max-messages N     Limit messages processed per mailbox per run (0 = unlimited)
+  -h, --help               Show help message
 ```
 
 ### Folder Pattern Examples
@@ -382,7 +383,7 @@ Complex setup with multiple accounts, filtering, and different sync modes:
 - Schedule regular backups of CouchDB databases
 
 ### Performance Tuning
-- Use `--max-messages` to limit processing load
+- Use `--max-messages`/`-m` to limit processing load
 - Run during off-peak hours for large initial syncs
 - Monitor IMAP server rate limits and connection limits
 - Consider running multiple instances for different accounts
@@ -408,7 +409,7 @@ Complex setup with multiple accounts, filtering, and different sync modes:
 
 **Performance Problems**:
 - Use date filtering (`since`) for large mailboxes
-- Implement `--max-messages` limits for initial syncs
+- Implement `--max-messages`/`-m` limits for initial syncs
 - Monitor server-side rate limiting
 
 For detailed troubleshooting, see the [test environment documentation](test/README.md).

go/config/config.go

@@ -2,10 +2,11 @@ package config
 
 import (
 	"encoding/json"
-	"flag"
 	"fmt"
 	"os"
 	"path/filepath"
+
+	"github.com/spf13/pflag"
 )
 
 type Config struct {
@@ -87,23 +88,37 @@ type CommandLineArgs struct {
 	MaxMessages int
 }
 
-// ParseCommandLine parses command line arguments
+// ParseCommandLine parses command line arguments using GNU-style options
 func ParseCommandLine() *CommandLineArgs {
-	configFlag := flag.String("config", "", "Path to configuration file")
-	maxMessagesFlag := flag.Int("max-messages", 0, "Maximum number of messages to process per mailbox per run (0 = no limit)")
-	flag.Parse()
+	var args CommandLineArgs
 
-	return &CommandLineArgs{
-		ConfigPath:  *configFlag,
-		MaxMessages: *maxMessagesFlag,
+	// Define long options with -- and short options with -
+	pflag.StringVarP(&args.ConfigPath, "config", "c", "", "Path to configuration file")
+	pflag.IntVarP(&args.MaxMessages, "max-messages", "m", 0, "Maximum number of messages to process per mailbox per run (0 = no limit)")
+	
+	// Add help option
+	pflag.BoolP("help", "h", false, "Show help message")
+	
+	pflag.Parse()
+
+	// Handle help flag
+	if help, _ := pflag.CommandLine.GetBool("help"); help {
+		fmt.Fprintf(os.Stderr, "mail2couch - Email backup utility for CouchDB\n\n")
+		fmt.Fprintf(os.Stderr, "Usage: %s [OPTIONS]\n\n", os.Args[0])
+		fmt.Fprintf(os.Stderr, "Options:\n")
+		pflag.PrintDefaults()
+		os.Exit(0)
 	}
+
+	return &args
 }
 
 // FindConfigFile searches for config.json in the following order:
-// 1. Path specified by -config flag
+// 1. Path specified by --config/-c flag
 // 2. ./config.json (current directory)
-// 3. ~/.config/mail2couch/config.json (user config directory)
-// 4. ~/.mail2couch.json (user home directory)
+// 3. ./config/config.json (config subdirectory)
+// 4. ~/.config/mail2couch/config.json (user config directory)
+// 5. ~/.mail2couch.json (user home directory)
 func FindConfigFile(args *CommandLineArgs) (string, error) {
 	if args.ConfigPath != "" {
 		if _, err := os.Stat(args.ConfigPath); err == nil {

go/go.mod

@@ -6,6 +6,7 @@ require (
 	github.com/emersion/go-imap/v2 v2.0.0-beta.5
 	github.com/emersion/go-message v0.18.1
 	github.com/go-kivik/kivik/v4 v4.4.0
+	github.com/spf13/pflag v1.0.7
 )
 
 require (

go/go.sum

@@ -24,6 +24,8 @@ github.com/pkg/errors v0.9.1 h1:FEBLx1zS214owpjy7qsBeixbURkuhQAwrK5UwLGTwt4=
 github.com/pkg/errors v0.9.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
 github.com/pmezard/go-difflib v1.0.1-0.20181226105442-5d4384ee4fb2 h1:Jamvg5psRIccs7FGNTlIRMkT8wgtp5eCXdBlqhYGL6U=
 github.com/pmezard/go-difflib v1.0.1-0.20181226105442-5d4384ee4fb2/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/spf13/pflag v1.0.7 h1:vN6T9TfwStFPFM5XzjsvmzZkLuaLX+HS+0SeFLRgU6M=
+github.com/spf13/pflag v1.0.7/go.mod h1:McXfInJRrz4CZXVZOBLb0bTZqETkiAhM9Iw0y3An2Bg=
 github.com/yuin/goldmark v1.4.13/go.mod h1:6yULJ656Px+3vBD8DxQVa3kxgyrAnzto9xy5taEt/CY=
 gitlab.com/flimzy/testy v0.14.0 h1:2nZV4Wa1OSJb3rOKHh0GJqvvhtE03zT+sKnPCI0owfQ=
 gitlab.com/flimzy/testy v0.14.0/go.mod h1:m3aGuwdXc+N3QgnH+2Ar2zf1yg0UxNdIaXKvC5SlfMk=

test/run-tests.sh

@@ -83,7 +83,7 @@ cd ../test
 
 # Run mail2couch with test configuration
 print_status "Running mail2couch with test configuration..."
-../go/mail2couch -config config-test.json -max-messages 3
+../go/mail2couch --config config-test.json --max-messages 3
 
 # Verify results
 print_status "Verifying test results..."
@@ -112,7 +112,7 @@ done
 
 # Test sync mode by running again (should show incremental behavior)
 print_status "Running mail2couch again to test incremental sync..."
-../go/mail2couch -config config-test.json -max-messages 3
+../go/mail2couch --config config-test.json --max-messages 3
 
 print_status "🎉 Basic integration tests completed successfully!"
 

test/test-incremental-sync.sh

@@ -67,7 +67,7 @@ build_app() {
 run_first_sync() {
     echo -e "\n${BLUE}Running first sync...${NC}"
     cd go
-    ./mail2couch -config ../test/config-test.json -max-messages 5
+    ./mail2couch --config ../test/config-test.json --max-messages 5
     cd ..
 }
 
@@ -138,7 +138,7 @@ EOF
 run_incremental_sync() {
     echo -e "\n${BLUE}Running incremental sync...${NC}"
     cd go
-    ./mail2couch -config ../test/config-test.json -max-messages 10
+    ./mail2couch --config ../test/config-test.json --max-messages 10
     cd ..
 }
 

test/test-wildcard-patterns.sh

@@ -31,7 +31,7 @@ run_test() {
     
     # Run mail2couch and capture output
     cd go
-    if ./mail2couch -config "../test/$config_file" -max-messages "$max_messages" 2>&1; then
+    if ./mail2couch --config "../test/$config_file" --max-messages "$max_messages" 2>&1; then
         echo -e "${GREEN}✅ Test completed successfully${NC}"
     else
         echo -e "${RED}❌ Test failed${NC}"