Use getTimestamp instead of getCurrentTime in writers.

Setting SOURCE_DATE_EPOCH will allow reproducible builds.

Partially addresses #7093.  This does not suffice to fully enable
reproducible in EPUB, since a unique id is being generated for each
build.

src/Text/Pandoc/Readers/RST.hs

@@ -28,7 +28,7 @@ import qualified Data.Text as T
 import Text.Pandoc.Builder (Blocks, Inlines, fromList, setMeta, trimInlines)
 import qualified Text.Pandoc.Builder as B
 import Text.Pandoc.Class.PandocMonad (PandocMonad, fetchItem,
-                                      readFileFromDirs, getCurrentTime)
+                                      readFileFromDirs, getTimestamp)
 import Text.Pandoc.CSV (CSVOptions (..), defaultCSVOptions, parseCSV)
 import Text.Pandoc.Definition
 import Text.Pandoc.Error
@@ -685,7 +685,7 @@ directive' = do
         "replace" -> B.para <$>  -- consumed by substKey
                    parseInlineFromText (trim top)
         "date" -> B.para <$> do  -- consumed by substKey
-                     t <- getCurrentTime
+                     t <- getTimestamp
                      let format = case T.unpack (T.strip top) of
                                     [] -> "%Y-%m-%d"
                                     x  -> x

src/Text/Pandoc/Writers/Docx.hs

@@ -217,7 +217,7 @@ writeDocx opts doc = do
   let doc' = Pandoc meta blocks'
 
   username <- P.lookupEnv "USERNAME"
-  utctime <- P.getCurrentTime
+  utctime <- P.getTimestamp
   oldUserDataDir <- P.getUserDataDir
   P.setUserDataDir Nothing
   res <- P.readDefaultDataFile "reference.docx"

src/Text/Pandoc/Writers/EPUB.hs

@@ -191,7 +191,7 @@ getEPUBMetadata opts meta = do
   let fixDate m =
        if null (epubDate m)
           then do
-            currentTime <- lift P.getCurrentTime
+            currentTime <- lift P.getTimestamp
             return $ m{ epubDate = [ Date{
                              dateText = showDateTimeISO8601 currentTime
                            , dateEvent = Nothing } ] }
@@ -709,7 +709,7 @@ pandocToEPUB version opts doc = do
   uuid <- case epubIdentifier metadata of
             (x:_) -> return $ identifierText x  -- use first identifier as UUID
             []    -> throwError $ PandocShouldNeverHappenError "epubIdentifier is null"  -- shouldn't happen
-  currentTime <- lift P.getCurrentTime
+  currentTime <- lift P.getTimestamp
   let contentsData = UTF8.fromStringLazy $ ppTopElement $
         unode "package" !
           ([("version", case version of

src/Text/Pandoc/Writers/ODT.hs

@@ -68,7 +68,7 @@ pandocToODT :: PandocMonad m
 pandocToODT opts doc@(Pandoc meta _) = do
   let title = docTitle meta
   let authors = docAuthors meta
-  utctime <- P.getCurrentTime
+  utctime <- P.getTimestamp
   lang <- toLang (getLang opts meta)
   refArchive <-
        case writerReferenceDoc opts of

src/Text/Pandoc/Writers/Powerpoint/Output.hs

@@ -312,7 +312,7 @@ presentationToArchive opts pres = do
                      Nothing -> toArchive . BL.fromStrict <$>
                         P.readDataFile "reference.pptx"
 
-  utctime <- P.getCurrentTime
+  utctime <- P.getTimestamp
 
   presSize <- case getPresentationSize refArchive distArchive of
                 Just sz -> return sz