Adds an isRelativePath to determine if path is relative

This PR adds an `isRelativePath` function to ign-common Filesystem.hh. It is a simple wrapper around `std::filesystem`.  The rationale for this is so we can remove `std::Filesystem` from ign-gazebo as this is causing other issues such as gazebo-tooling/release-tools#639.

Signed-off-by: Arjo Chakravarty <[email protected]>

include/ignition/common/Filesystem.hh

@@ -57,6 +57,11 @@ namespace ignition
     /// \return True if _path is a file.
     bool IGNITION_COMMON_VISIBLE isFile(const std::string &_path);
 
+    /// \brief Check if the given path is relative.
+    /// \param[in] _path Path.
+    /// \return True if _path is relative.
+    bool IGNITION_COMMON_VISIBLE isRelativePath(const std::string &_path);
+
     /// \brief Create a new directory on the filesystem.  Intermediate
     ///        directories must already exist.
     /// \param[in] _path  The new directory path to create

src/Filesystem.cc

@@ -71,6 +71,12 @@ bool ignition::common::isFile(const std::string &_path)
   return fs::is_regular_file(_path);
 }
 
+/////////////////////////////////////////////////
+bool ignition::common::isRelativePath(const std::string &_path)
+{
+  return fs::path(_path).is_relative();
+}
+
 /////////////////////////////////////////////////
 bool ignition::common::createDirectory(const std::string &_path)
 {