Print out all attempted paths

When trying to look up paths passed to `--affected` we attempt to
convert to absolute and relative paths in case the Ninja input file does
not match how files were passed in.

When this fails, it would be nice to let the user know that other file
paths were tried.  It is a good reminder what base path is used when
converting from relative to absolute paths.

src/trimutil.cpp

@@ -643,11 +643,14 @@ void TrimUtil::trim(std::ostream& output,
   }
 
   // Mark all files in `affected` as required
+  std::vector<std::filesystem::path> attempted;
   for (std::string line; std::getline(affected, line);) {
     if (line.empty()) {
       continue;
     }
 
+    attempted.clear();
+
     // First try the raw input
     {
       const std::optional<std::size_t> index = graph.findPath(line);
@@ -666,7 +669,8 @@ void TrimUtil::trim(std::ostream& output,
     std::filesystem::path p(line);
     if (!p.is_absolute()) {
       std::error_code okay;
-      const std::filesystem::path absolute = std::filesystem::absolute(p, okay);
+      const std::filesystem::path& absolute =
+          attempted.emplace_back(std::filesystem::absolute(p, okay));
       if (okay) {
         std::string absoluteStr = absolute.string();
         const std::optional<std::size_t> index = graph.findPath(absoluteStr);
@@ -686,7 +690,8 @@ void TrimUtil::trim(std::ostream& output,
     // file
     if (!p.is_relative()) {
       std::error_code okay;
-      const std::filesystem::path relative = std::filesystem::relative(p, okay);
+      const std::filesystem::path& relative =
+          attempted.emplace_back(std::filesystem::relative(p, okay));
       if (okay) {
         std::string relativeStr = relative.string();
         const std::optional<std::size_t> index = graph.findPath(relativeStr);
@@ -702,7 +707,17 @@ void TrimUtil::trim(std::ostream& output,
       }
     }
 
-    std::cerr << "'" << line << "' not found in input file" << std::endl;
+    std::cerr << "'" << line << "' not found in input file";
+    if (!attempted.empty()) {
+      std::cerr << " (also tried ";
+      const char* separator = "";
+      for (const std::filesystem::path& path : attempted) {
+        std::cerr << separator << "'" << path.string() << "'";
+        separator = ", ";
+      }
+      std::cerr << ')';
+    }
+    std::cerr << std::endl;
   }
 
   std::vector<bool> seen(graph.size());