Fix handling of symbolic links on Linux

When a file is a symbolic link to some other file the proper behavior
when calculating the checksum of a package is to use the link path
instead of the content of the pointed file.

Additionally the `getPackageFileListWithoutVcs` procedure is fixed to
return also the symbolic link files.

Related to nim-lang#127

src/nimblepkg/checksums.nim

@@ -25,22 +25,36 @@ proc updateSha1Checksum(checksum: var Sha1State, fileName, filePath: string) =
     # directory from which no files are being installed.
     return
   checksum.update(fileName)
-  var file: File
-  try:
-    file = filePath.open(fmRead)
-  except IOError:
-    ## If the file cannot be open for reading do not count its content in the
-    ## checksum.
-    displayWarning(&"The file \"{filePath}\" cannot be open for reading.\n" &
-                    "Skipping it in the calculation of the checksum.")
-    return
-  defer: close(file)
-  const bufferSize = 8192
-  var buffer = newString(bufferSize)
-  while true:
-    var bytesRead = readChars(file, buffer)
-    if bytesRead == 0: break
-    checksum.update(buffer.toOpenArray(0, bytesRead - 1))
+  if symlinkExists(filePath):
+    # Check whether a file is a symbolic link and if so update the checksum with
+    # the path to the file that the link points to.
+    var linkPath: string
+    try:
+      linkPath = expandSymlink(filePath)
+    except OSError:
+      displayWarning(&"Cannot expand symbolic link \"{filePath}\".\n" &
+                      "Skipping it in the calculation of the checksum.")
+      return
+    checksum.update(linkPath)
+  else:
+    # Otherwise this is an ordinary file and we are adding its content to the
+    # checksum.
+    var file: File
+    try:
+      file = filePath.open(fmRead)
+    except IOError:
+      ## If the file cannot be open for reading do not count its content in the
+      ## checksum.
+      displayWarning(&"The file \"{filePath}\" cannot be open for reading.\n" &
+                      "Skipping it in the calculation of the checksum.")
+      return
+    defer: close(file)
+    const bufferSize = 8192
+    var buffer = newString(bufferSize)
+    while true:
+      var bytesRead = readChars(file, buffer)
+      if bytesRead == 0: break
+      checksum.update(buffer.toOpenArray(0, bytesRead - 1))
 
 proc calculateDirSha1Checksum*(dir: string): Sha1Hash =
   ## Recursively calculates the sha1 checksum of the contents of the directory

src/nimblepkg/vcstools.nim

@@ -203,7 +203,8 @@ proc getVcsRevision*(dir: Path): Sha1Hash =
 proc getPackageFileListWithoutVcs(dir: Path): seq[string] =
   ## Recursively walks the directory `dir` and returns a list of files in it and
   ## its subdirectories.
-  for file in walkDirRec($dir, relative = true):
+  for file in walkDirRec($dir, yieldFilter = {pcFile, pcLinkToFile},
+                         relative = true):
     result.add file
 
 proc getPackageFileList*(dir: Path): seq[string] =