reimplement path operations basename() and concat() in Common. these were the last bits remaining in ArchFile* so it was removed

src/lib/common/PathUtilities.cpp

@@ -0,0 +1,45 @@
+#include "PathUtilities.h"
+
+// keep the default platform delimiter as the first in the list
+#ifdef _WIN32
+static const char *Delimiters = "\\/";
+#else
+static const char *Delimiters = "/";
+#endif
+
+static const char DefaultDelimiter = Delimiters[0];
+
+std::string PathUtilities::basename(const std::string& path)
+{
+    return path.substr(path.find_last_of(Delimiters) + 1);
+}
+
+std::string PathUtilities::concat(const std::string& left, const std::string& right)
+{
+    // although npos is usually (-1) we can't count on that so handle it explicitly
+    auto leftEnd = left.find_last_not_of(Delimiters);
+    if (leftEnd == std::string::npos)
+        leftEnd = 0;
+    else
+        ++leftEnd;
+    auto rightStart = right.find_first_not_of(Delimiters, 0);
+    if (rightStart == std::string::npos) {
+        // l/r empty
+        if (left.size() == 0 && right.size() == 0)
+            return "";
+        // r useless, l okay
+        if (leftEnd > 0)
+            return left.substr(0, leftEnd);
+        // both useless but one has a delim
+        return std::string(1, DefaultDelimiter);
+    }
+    if (leftEnd == 0) {
+        // r okay and not prefixed with delims, l empty
+        if (left.size() == 0 && rightStart == 0)
+            return right.substr(rightStart);
+        // r okay and prefixed with delims OR l full of delims
+        return DefaultDelimiter + right.substr(rightStart);
+    }
+    // normal concatenation
+    return left.substr(0, leftEnd) + DefaultDelimiter + right.substr(rightStart);
+}