on conflicting fields. This changes earlier behavior (but not in
a release), where first took precedence.
Note that this may seem inconsistent with the behavior of
multiple YAML blocks within a document, where the first takes
precedence. Still, it is convenient to be able to override
defaults with options later on the command line.
Changed optMetadataFile from `Maybe FilePath` to `[FilePath]`. This allows
for multiple YAML metadata files to be added. The new default value has
been changed from `Nothing` to `[]`.
To account for this change in `Text.Pandoc.App`, `metaDataFromFile` now
operates on two `mapM` calls (for `readFileLazy` and `yamlToMeta`) and a fold.
Added a test (command/5700.md) which tests this functionality and
updated MANUAL.txt, as per the contributing guidelines.
With the current behavior, using `foldr1 (<>)`, values within files
specified first will be used over those in later files. (If the reverse
of this behavior would be preferred, it should be fixed by changing
foldr1 to foldl1.)
