nimsuggest: when invoked with a directory, detect the main nim file on its own

compiler/options.nim

@@ -392,6 +392,23 @@ proc findModule*(modulename, currentModule: string): string =
     result = findFile(m)
   patchModule()
 
+proc findProjectNimFile*(pkg: string): string =
+  const extensions = [".nims", ".cfg", ".nimcfg", ".nimble"]
+  var candidates: seq[string] = @[]
+  for k, f in os.walkDir(pkg, relative=true):
+    if k == pcFile and f != "config.nims":
+      let (_, name, ext) = splitFile(f)
+      if ext in extensions:
+        let x = changeFileExt(pkg / name, ".nim")
+        if fileExists(x):
+          candidates.add x
+  for c in candidates:
+    # nim-foo foo  or  foo  nfoo
+    if (pkg in c) or (c in pkg): return c
+  if candidates.len >= 1:
+    return candidates[0]
+  return ""
+
 proc canonDynlibName(s: string): string =
   let start = if s.startsWith("lib"): 3 else: 0
   let ende = strutils.find(s, {'(', ')', '.'})