fs/Traits: convert first Relative() parameter to std::string_view

src/fs/Traits.cxx

@@ -86,10 +86,9 @@ GetParentPathImpl(typename Traits::const_pointer p) noexcept
 
 template<typename Traits>
 typename Traits::const_pointer
-RelativePathImpl(typename Traits::const_pointer base,
+RelativePathImpl(typename Traits::string_view base,
 		 typename Traits::const_pointer other) noexcept
 {
-	assert(base != nullptr);
 	assert(other != nullptr);
 
 	other = StringAfterPrefix(other, base);
@@ -99,7 +98,7 @@ RelativePathImpl(typename Traits::const_pointer base,
 
 	if (*other != 0) {
 		if (!Traits::IsSeparator(*other)) {
-			if (*base != 0 && Traits::IsSeparator(other[-1]))
+			if (!base.empty() && Traits::IsSeparator(other[-1]))
 				/* "other" has no more slash, but the
 				   matching base ended with a slash:
 				   enough to detect a match */
@@ -137,7 +136,7 @@ PathTraitsFS::GetParent(PathTraitsFS::const_pointer p) noexcept
 }
 
 PathTraitsFS::const_pointer
-PathTraitsFS::Relative(const_pointer base, const_pointer other) noexcept
+PathTraitsFS::Relative(string_view base, const_pointer other) noexcept
 {
 	return RelativePathImpl<PathTraitsFS>(base, other);
 }
@@ -175,8 +174,7 @@ PathTraitsUTF8::GetParent(const_pointer p) noexcept
 }
 
 PathTraitsUTF8::const_pointer
-PathTraitsUTF8::Relative(const_pointer base,
-			 const_pointer other) noexcept
+PathTraitsUTF8::Relative(string_view base, const_pointer other) noexcept
 {
 	return RelativePathImpl<PathTraitsUTF8>(base, other);
 }

src/fs/Traits.hxx

@@ -147,8 +147,7 @@ struct PathTraitsFS {
 	 * nullptr on mismatch.
 	 */
 	gcc_pure gcc_nonnull_all
-	static const_pointer Relative(const_pointer base,
-				      const_pointer other) noexcept;
+	static const_pointer Relative(string_view base, const_pointer other) noexcept;
 
 	/**
 	 * Constructs the path from the given components.
@@ -256,8 +255,7 @@ struct PathTraitsUTF8 {
 	 * nullptr on mismatch.
 	 */
 	gcc_pure gcc_nonnull_all
-	static const_pointer Relative(const_pointer base,
-				      const_pointer other) noexcept;
+	static const_pointer Relative(string_view base, const_pointer other) noexcept;
 
 	/**
 	 * Constructs the path from the given components.

src/storage/plugins/CurlStorage.cxx

@@ -81,7 +81,7 @@ CurlStorage::MapUTF8(const char *uri_utf8) const noexcept
 const char *
 CurlStorage::MapToRelativeUTF8(const char *uri_utf8) const noexcept
 {
-	return PathTraitsUTF8::Relative(base.c_str(),
+	return PathTraitsUTF8::Relative(base,
 					CurlUnescape(uri_utf8).c_str());
 }
 

src/storage/plugins/LocalStorage.cxx

@@ -129,7 +129,7 @@ LocalStorage::MapFS(const char *uri_utf8) const noexcept
 const char *
 LocalStorage::MapToRelativeUTF8(const char *uri_utf8) const noexcept
 {
-	return PathTraitsUTF8::Relative(base_utf8.c_str(), uri_utf8);
+	return PathTraitsUTF8::Relative(base_utf8, uri_utf8);
 }
 
 StorageFileInfo

src/storage/plugins/NfsStorage.cxx

@@ -246,7 +246,7 @@ NfsStorage::MapUTF8(const char *uri_utf8) const noexcept
 const char *
 NfsStorage::MapToRelativeUTF8(const char *uri_utf8) const noexcept
 {
-	return PathTraitsUTF8::Relative(base.c_str(), uri_utf8);
+	return PathTraitsUTF8::Relative(base, uri_utf8);
 }
 
 static void

src/storage/plugins/SmbclientStorage.cxx

@@ -87,7 +87,7 @@ SmbclientStorage::MapUTF8(const char *uri_utf8) const noexcept
 const char *
 SmbclientStorage::MapToRelativeUTF8(const char *uri_utf8) const noexcept
 {
-	return PathTraitsUTF8::Relative(base.c_str(), uri_utf8);
+	return PathTraitsUTF8::Relative(base, uri_utf8);
 }
 
 static StorageFileInfo

src/storage/plugins/UdisksStorage.cxx

@@ -347,7 +347,7 @@ UdisksStorage::MapUTF8(const char *uri_utf8) const noexcept
 const char *
 UdisksStorage::MapToRelativeUTF8(const char *uri_utf8) const noexcept
 {
-	return PathTraitsUTF8::Relative(base_uri.c_str(), uri_utf8);
+	return PathTraitsUTF8::Relative(base_uri, uri_utf8);
 }
 
 static std::unique_ptr<Storage>