fix: don't strip prefix if path is exactly "." (#293)

One of the things I often run is "yr scan -r rules.yara ." when I have a
collection of samples and I want to scan all of them in the current directory.

With the fix in #280 the path was being stripped to an empty string which would
result in an error when trying to scan. Fix it by only performing the strip if
the path is not equal to ".".

cli/src/tests/mod.rs

@@ -284,4 +284,13 @@ fn cli_issue_280() {
         .arg("./src/tests/testdata/")
         .assert()
         .success();
+
+    // Handle special case of just . for path argument.
+    Command::cargo_bin("yr")
+        .unwrap()
+        .arg("scan")
+        .arg("src/tests/testdata/foo.yar")
+        .arg(".")
+        .assert()
+        .success();
 }

cli/src/walk.rs

@@ -203,12 +203,20 @@ impl<'a> Walker<'a> {
         // workaround for a bug in globwalk that causes a panic.
         // https://github.com/VirusTotal/yara-x/issues/280
         // https://github.com/Gilnaa/globwalk/issues/28
-
-        #[cfg(not(target_os = "windows"))]
-        let path = self.path.strip_prefix("./").unwrap_or(self.path);
-
-        #[cfg(target_os = "windows")]
-        let path = self.path.strip_prefix(r#".\"#).unwrap_or(self.path);
+        //
+        // Only perform the strip if the path is not exactly "." - this allows
+        // users to run "yr scan rules.yara ." to scan all the files in the
+        // current directory.
+        let path = if self.path.as_os_str().ne(".") {
+            #[cfg(not(target_os = "windows"))]
+            let path = self.path.strip_prefix("./").unwrap_or(self.path);
+
+            #[cfg(target_os = "windows")]
+            let path = self.path.strip_prefix(r#".\"#).unwrap_or(self.path);
+            path
+        } else {
+            self.path
+        };
 
         let mut builder = if self.filters.is_empty() {
             globwalk::GlobWalkerBuilder::from_patterns(path, &["**"])