added --timestamp option

Author: datsom1

README.md

@@ -35,6 +35,7 @@
 - Compare CSV, TSV, and JSON files for differences
 - Human-readable and machine-readable (JSON) output
 - JSON output to file with filename and path support
+- Optional timestamp in output filenames
 - Detects added, removed, and changed rows and columns
 - Supports custom key columns for row identity
 - Field inclusion/exclusion for focused diffs
@@ -279,6 +280,7 @@ A summary of key options:
 | `--output TEXT`       | Output format: `readable`, `json`, or `jsonfile` (default: readable)                         |
 | `--outfilename FILE`  | File to write JSON output to (used with `--output=jsonfile`)                                 |
 | `--outfilepath DIR`   | Directory to save the output file (used with `--output=jsonfile`)                            |
+| `--timestamp TEXT`    | Include timestamp in output filename: `true` or `false` (default: true)                      |
 | `--fields TEXT`       | Comma-separated list of fields to compare (all others ignored)                               |
 | `--ignorefields TEXT` | Comma-separated list of fields to ignore during comparison                                   |
 | `--showunchanged`     | Show all fields for changed records, not just changed fields                                 |
@@ -312,6 +314,12 @@ db-diff one.csv two.csv --key=Id --output=json
 db-diff one.csv two.csv --key=Id --output=jsonfile --outfilename=diffs.json
 ```
 
+**Save JSON output without timestamp in filename:**
+
+```sh
+db-diff one.csv two.csv --key=Id --output=jsonfile --timestamp=false
+```
+
 **Compare only specific fields:**
 
 ```sh

db_diff/cli.py

@@ -115,7 +115,8 @@ def load(filename: str, key: str, input_format: str, encoding: str = "utf-8") ->
         raise click.ClickException(f"Failed to load '{filename}': {e}")
 
 def generate_output_filename(previous: str, current: str, output_file: Optional[str], 
-                         output_path: Optional[str], timestamp: Optional[str] = None) -> str:
+                         output_path: Optional[str], timestamp: Optional[str] = None,
+                         use_timestamp: bool = True) -> str:
     """
     Generate an output filename for the diff result.
     
@@ -125,27 +126,33 @@ def generate_output_filename(previous: str, current: str, output_file: Optional[
         output_file: User-specified output filename (optional)
         output_path: User-specified output directory (optional)
         timestamp: Timestamp to use (optional)
+        use_timestamp: Whether to include timestamp in filename (default: True)
         
     Returns:
         Full path to the output file
         
     Raises:
         click.ClickException: If the output path doesn't exist
     """
-    if timestamp is None:
-        timestamp = datetime.datetime.now().strftime("%Y-%m-%d_%H-%M-%S")
+    timestamp_prefix = ""
+    if use_timestamp:
+        if timestamp is None:
+            timestamp = datetime.datetime.now().strftime("%Y-%m-%d_%H-%M-%S")
+        timestamp_prefix = f"{timestamp}_"
 
     # Extract base filenames without extensions for the comparison files
     prev_basename = os.path.splitext(os.path.basename(previous))[0]
     curr_basename = os.path.splitext(os.path.basename(current))[0]
 
     if not output_file:
         # Default output filename
-        output_file = f"{timestamp}_diffs_{prev_basename}__VS__{curr_basename}.json"
+        output_file = f"{timestamp_prefix}diffs_{prev_basename}__vs__{curr_basename}.json"
     else:
-        # Append the user-specified filename to the timestamp
-        base_name = os.path.splitext(output_file)[0]  # Remove extension if present
-        output_file = f"{timestamp}_diffs_{base_name}.json"
+        # Prepend the timestamp to the user-specified filename if needed
+        output_file = f"{timestamp_prefix}diffs_{output_file}"
+        # Ensure the output file has a .json extension
+        if not output_file.endswith('.json'):
+            output_file += '.json'
 
     # Handle output path
     if output_path:
@@ -170,6 +177,8 @@ def generate_output_filename(previous: str, current: str, output_file: Optional[
            "\n     db-diff old.csv new.csv --key=Id\n"
            "\n Output to JSON file:\n"
            "\n     db-diff old.csv new.csv --output=jsonfile --outfilename=diff.json\n"
+           "\n Output without timestamp in filename:\n"
+           "\n     db-diff old.csv new.csv --output=jsonfile --timestamp=false\n"
            "\n Compare only specific fields:\n"
            "\n     db-diff old.csv new.csv --fields=Id,Name,Email\n"
            "\n Ignore specific fields:\n"
@@ -206,7 +215,7 @@ def generate_output_filename(previous: str, current: str, output_file: Optional[
     "output_file",
     type=click.Path(file_okay=True, dir_okay=False, writable=True, resolve_path=True),
     default=None,
-    help="File to write JSON output to. [default: YYYY-MM-DD_HH-MM-SS_diffs_file1name__VS__file2name.json]",
+    help="Specify custom filename. [default: diffs_<filename1__vs__filename2>.json]",
 )
 @click.option(
     "--outfilepath",
@@ -264,11 +273,18 @@ def generate_output_filename(previous: str, current: str, output_file: Optional[
     is_flag=True,
     help="Enable verbose output.",
 )
+@click.option(
+    "--timestamp",
+    type=click.Choice(["true", "false"], case_sensitive=False),
+    default="false",
+    show_default=True,
+    help="Add timestamp to filename: YYYY-MM-DD_HH-MM-SS_diffs_<filename>.json",
+)
 @click.version_option()
 def cli(
     previous, current, key, input_format,
     show_unchanged, encoding, output, output_file, output_path,
-    fields, ignorefields, streaming, listfields, verbose
+    fields, ignorefields, streaming, listfields, verbose, timestamp
 ):
     """Compare the differences between two CSV or JSON files."""
     # Set logging level based on verbosity
@@ -323,7 +339,8 @@ def cli(
     # Set default output filename if needed
     if output == "jsonfile":
         try:
-            output_file = generate_output_filename(previous, current, output_file, output_path)
+            use_timestamp = timestamp.lower() == "true"
+            output_file = generate_output_filename(previous, current, output_file, output_path, use_timestamp=use_timestamp)
         except Exception as e:
             raise click.ClickException(f"Failed to generate output filename: {e}")