fix #6583, fix #14376, index+search now generated for all projects, many bug fixes with nim doc (#14324)

* refs #6583 fix nim doc output
* changelog
* change default for outDir when unspecified
* cleanups
* --project implies --index

compiler/options.nim

@@ -9,7 +9,7 @@
 
 import
   os, strutils, strtabs, sets, lineinfos, platform,
-  prefixmatches, pathutils
+  prefixmatches, pathutils, nimpaths
 
 from terminal import isatty
 from times import utc, fromUnix, local, getTime, format, DateTime
@@ -518,8 +518,9 @@ const
   DefaultConfigNims* = RelativeFile"config.nims"
   DocConfig* = RelativeFile"nimdoc.cfg"
   DocTexConfig* = RelativeFile"nimdoc.tex.cfg"
-
-const oKeepVariableNames* = true
+  htmldocsDir* = htmldocsDirname.RelativeDir
+  docRootDefault* = "@default" # using `@` instead of `$` to avoid shell quoting complications
+  oKeepVariableNames* = true
 
 proc mainCommandArg*(conf: ConfigRef): string =
   ## This is intended for commands like check or parse
@@ -543,6 +544,7 @@ proc getOutFile*(conf: ConfigRef; filename: RelativeFile, ext: string): Absolute
   # explains regression https://github.com/nim-lang/Nim/issues/6583#issuecomment-625711125
   # Yet another reason why "" should not mean ".";  `""/something` should raise
   # instead of implying "" == "." as it's bug prone.
+  doAssert conf.outDir.string.len > 0
   result = conf.outDir / changeFileExt(filename, ext)
 
 proc absOutFile*(conf: ConfigRef): AbsoluteFile =