Allow --resource-path to accumulate.

Previously, if `--resource-path` were used multiple times, the last
resource path would replace the others.

With this change, each time `--resource-path` is used, it prepends
the specified path components to the existing resource path.

Similarly, when `resource-path` is specified in a defaults file,
the paths provided will be prepended to the existing resource
path.

This change also allows one to avoid using the OS-specific path
separator; instead, one can simply use `--resource-path`
a number of times with single paths. This form of command
will not have an OS-dependent behavior.

This change facilitates the use of multiple, small defaults
files: each can specify a directory containing its own
resources without clobbering the resource paths set by
the others.

Closes #6152.

MANUAL.txt

@@ -891,6 +891,11 @@ header when requesting a document from a URL:
     will not be searched.  For example:
     `--resource-path=.:test` will search the working directory
     and the `test` subdirectory, in that order.
+    This option can be used repeatedly. Search path components
+    that come later on the command line will be searched before
+    those that come earlier, so
+    `--resource-path foo:bar --resource-path baz:bim` is
+    equivalent to `--resource-path baz:bim:foo:bar`.
 
 `--request-header=`*NAME*`:`*VAL*
 

src/Text/Pandoc/App/CommandLineOptions.hs

@@ -288,7 +288,8 @@ options =
     , Option "" ["resource-path"]
                 (ReqArg
                   (\arg opt -> return opt { optResourcePath =
-                                   splitSearchPath arg })
+                                   splitSearchPath arg ++
+                                    optResourcePath opt })
                    "SEARCHPATH")
                   "" -- "Paths to search for images and other resources"
 

src/Text/Pandoc/App/Opt.hs

@@ -583,7 +583,8 @@ doOpt (k',v) = do
                                 optIncludeInHeader o <> [unpack x] }))
     "resource-path" ->
       parseYAML v >>= \x ->
-             return (\o -> o{ optResourcePath = map unpack x })
+             return (\o -> o{ optResourcePath = map unpack x <>
+                                 optResourcePath o })
     "request-headers" ->
       parseYAML v >>= \x ->
              return (\o -> o{ optRequestHeaders = x })