Allow boolean flags to be repeated

bat prepends the arguments from its config file to the command line, so a
user who has `--show-all` in their config and also types `-A` passes the
flag twice, and clap rejects that with "the argument '--show-all' cannot be
used multiple times" and exit code 2. The file is never displayed.

`--plain`, `--number`, `--number-nonblank`, `--force-colorization` and
`--no-paging` already avoid this by overriding themselves. The same is now
done for the eight remaining flags that affect how a file is displayed:
--show-all, --diff, --chop-long-lines, --squeeze-blank, --unbuffered,
--quiet-empty, --no-custom-assets and --set-terminal-title.

Repeating a flag produces byte-identical output to giving it once, and
--show-all still conflicts with --language as before.

CHANGELOG.md

@@ -25,6 +25,7 @@
 - Syntax highlighting for Python files using uv as script runner in shebang #3689 (@janlarres)
 
 ## Bugfixes
+- Allow boolean flags to be given more than once, so that a flag set in the config file can also be passed on the command line without erroring, see #3912 (@logarithmone1128)
 - Use parsed CLI arguments to detect number flags, see #3908 (@cuishuang)
 - Detect binary content beyond the first line, preventing encrypted files with early line breaks from being treated as text. Closes #3554, see #3877 (@Matei02355)
 - Use the last occurrence of numbering and plain flags in combined short arguments, see #3897 (@cuishuang)

src/bin/bat/clap_app.rs

@@ -52,6 +52,7 @@ pub fn build_app(interactive_output: bool) -> Command {
                 .long("show-all")
                 .alias("show-nonprintable")
                 .short('A')
+                .overrides_with("show-all")
                 .action(ArgAction::SetTrue)
                 .conflicts_with("language")
                 .help("Show non-printable characters (space, tab, newline, ..).")
@@ -171,6 +172,7 @@ pub fn build_app(interactive_output: bool) -> Command {
                     Arg::new("diff")
                         .long("diff")
                         .short('d')
+                        .overrides_with("diff")
                         .action(ArgAction::SetTrue)
                         .conflicts_with("line-range")
                         .help("Only show lines that have been added/removed/modified.")
@@ -235,6 +237,7 @@ pub fn build_app(interactive_output: bool) -> Command {
             Arg::new("chop-long-lines")
                 .long("chop-long-lines")
                 .short('S')
+                .overrides_with("chop-long-lines")
                 .action(ArgAction::SetTrue)
                 .help("Truncate all lines longer than screen width. Alias for '--wrap=never'."),
         )
@@ -473,6 +476,7 @@ pub fn build_app(interactive_output: bool) -> Command {
             Arg::new("squeeze-blank")
                 .long("squeeze-blank")
                 .short('s')
+                .overrides_with("squeeze-blank")
                 .action(ArgAction::SetTrue)
                 .help("Squeeze consecutive empty lines.")
                 .long_help("Squeeze consecutive empty lines into a single empty line.")
@@ -598,6 +602,7 @@ pub fn build_app(interactive_output: bool) -> Command {
             Arg::new("unbuffered")
                 .short('u')
                 .long("unbuffered")
+                .overrides_with("unbuffered")
                 .action(ArgAction::SetTrue)
                 .help("Enable unbuffered input reading for streaming use cases.")
                 .long_help(
@@ -619,6 +624,7 @@ pub fn build_app(interactive_output: bool) -> Command {
         .arg(
             Arg::new("no-custom-assets")
                 .long("no-custom-assets")
+                .overrides_with("no-custom-assets")
                 .action(ArgAction::SetTrue)
                 .hide(true)
                 .help("Do not load custom assets"),
@@ -699,6 +705,7 @@ pub fn build_app(interactive_output: bool) -> Command {
             Arg::new("quiet-empty")
                 .long("quiet-empty")
                 .short('E')
+                .overrides_with("quiet-empty")
                 .action(ArgAction::SetTrue)
                 .help("Produce no output when the input is empty.")
                 .long_help(
@@ -717,6 +724,7 @@ pub fn build_app(interactive_output: bool) -> Command {
         .arg(
             Arg::new("set-terminal-title")
                 .long("set-terminal-title")
+                .overrides_with("set-terminal-title")
                 .action(ArgAction::SetTrue)
                 .hide_short_help(true)
                 .help("Sets terminal title to filenames when using a pager."),

tests/examples/bat-show-all.conf

@@ -0,0 +1 @@
+--show-all

tests/integration_tests.rs

@@ -646,6 +646,30 @@ fn piped_output_with_default_style_flag() {
         );
 }
 
+#[test]
+fn repeated_boolean_flag_is_accepted() {
+    // A flag in the config file is prepended to the command line, so a user
+    // who has `--show-all` in their config and also types `-A` ends up passing
+    // it twice. That must not be an error.
+    bat()
+        .arg("empty_lines.txt")
+        .arg("--show-all")
+        .arg("--show-all")
+        .assert()
+        .success();
+}
+
+#[test]
+fn boolean_flag_in_config_and_on_command_line() {
+    bat_with_config()
+        .env("BAT_CONFIG_PATH", "bat-show-all.conf")
+        .arg("empty_lines.txt")
+        .arg("--show-all")
+        .arg("--paging=never")
+        .assert()
+        .success();
+}
+
 #[test]
 fn squeeze_blank() {
     bat()