Add support for fixed strings and --less-search-pattern

Previously, if you tried to use the `-F`/`--fixed strings` option for ripgrep in
combination with the `--less-search-pattern` option, `less` would either a)
match a different pattern than intended, since it would be interpreted as a
regular expression, or b) refuse to start if it detected an invalid pattern.

This change keeps track of whether or not the `--fixed-strings` option was
passed in. If both it and the `--less-search-pattern` was passed in, a `^R`
(Control-R) control character is prepended to the search pattern. This instructs
less to *not* treat the pattern as a regular expression.

src/batgrep.sh

@@ -31,6 +31,7 @@ OPT_FOLLOW=true
 OPT_SNIP=""
 OPT_HIGHLIGHT=true
 OPT_SEARCH_PATTERN=false
+OPT_FIXED_STRINGS=false
 BAT_STYLE="header,numbers"
 
 # Set options based on the bat version.
@@ -51,7 +52,8 @@ while shiftopt; do
 		-C|--context)        shiftval; OPT_CONTEXT_BEFORE="$OPT_VAL";
 			                           OPT_CONTEXT_AFTER="$OPT_VAL";;
 
-		-F|--fixed-strings|\
+		-F|--fixed-strings) OPT_FIXED_STRINGS=true; RG_ARGS+=("$OPT");;
+
 		-U|--multiline|\
 		-P|--pcre2|\
 		-z|--search-zip|\
@@ -138,7 +140,17 @@ if [[ "$OPT_CONTEXT_BEFORE" -eq 0 && "$OPT_CONTEXT_AFTER" -eq 0 ]]; then
 fi
 
 if [[ "$OPT_LESS_SEARCH_PATTERN" = true ]]; then
-    SCRIPT_PAGER_ARGS+=(-p "$PATTERN")
+	if [[ "$OPT_FIXED_STRINGS" = true ]]; then
+		# Depending on your editor, this may look identical. However, there is a
+		# special control character at the beginning of the pattern string, right
+		# after the first double quote. It is a a ^R, or Control-R, character. This
+		# instructs less to NOT use regular expressions, which is what the -F flag
+		# does for ripgrep. If we did not use this, then less would match a
+		# different pattern than ripgrep searched for.
+		SCRIPT_PAGER_ARGS+=(-p "$PATTERN")
+	else
+		SCRIPT_PAGER_ARGS+=(-p "$PATTERN")
+	fi
 fi
 
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