Add new '--blank' option for 'bat cache --init'

closes #206

assets/create.sh

@@ -2,4 +2,4 @@
 
 ASSET_DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"
 
-bat cache --init --source="$ASSET_DIR" --target="$ASSET_DIR"
+bat cache --init --blank --source="$ASSET_DIR" --target="$ASSET_DIR"

src/app.rs

@@ -210,6 +210,12 @@ impl App {
                             .help(
                                 "Use a different directory to store the cached syntax and theme set",
                             ),
+                    ).arg(
+                        Arg::with_name("blank")
+                            .long("blank")
+                            .requires("init")
+                            .help("Create completely new syntax and theme sets \
+                                   (instead of appending to the default sets")
                     ),
             ).help_message("Print this help message.")
             .version_message("Show version information.")

src/assets.rs

@@ -1,6 +1,7 @@
 use directories::ProjectDirs;
 use errors::*;
 use std::borrow::Cow;
+use std::collections::BTreeMap;
 use std::fs::{self, File};
 use std::path::{Path, PathBuf};
 use syntect::dumps::{dump_to_file, from_binary, from_reader};
@@ -25,10 +26,27 @@ impl HighlightingAssets {
         Self::from_cache().unwrap_or_else(|_| Self::from_binary())
     }
 
-    pub fn from_files(dir: Option<&Path>) -> Result<Self> {
+    fn empty() -> Self {
+        let mut syntax_set = SyntaxSet::new();
+        syntax_set.load_plain_text_syntax();
+
+        let theme_set = ThemeSet {
+            themes: BTreeMap::new(),
+        };
+        HighlightingAssets {
+            syntax_set,
+            theme_set,
+        }
+    }
+
+    pub fn from_files(dir: Option<&Path>, start_empty: bool) -> Result<Self> {
         let source_dir = dir.unwrap_or_else(|| PROJECT_DIRS.config_dir());
 
-        let mut assets = Self::from_binary_unlinked();
+        let mut assets = if start_empty {
+            Self::empty()
+        } else {
+            Self::from_binary_unlinked()
+        };
 
         let theme_dir = source_dir.join("themes");
 

src/main.rs

@@ -73,7 +73,9 @@ fn run() -> Result<bool> {
                 let source_dir = cache_matches.value_of("source").map(Path::new);
                 let target_dir = cache_matches.value_of("target").map(Path::new);
 
-                let assets = HighlightingAssets::from_files(source_dir)?;
+                let blank = cache_matches.is_present("blank");
+
+                let assets = HighlightingAssets::from_files(source_dir, blank)?;
                 assets.save(target_dir)?;
             } else if cache_matches.is_present("clear") {
                 clear_assets();