patch 8.1.0562: parsing of 'diffopt' is slightly wrong

Problem:    Parsing of 'diffopt' is slightly wrong.
Solution:   Fix the parsing and add a test. (Jason Franklin, Christian
            Brabandt)
diff --git a/src/testdir/dumps/Test_diff_09.dump b/src/testdir/dumps/Test_diff_09.dump
index 6445a57..95692b6 100644
--- a/src/testdir/dumps/Test_diff_09.dump
+++ b/src/testdir/dumps/Test_diff_09.dump
@@ -17,4 +17,4 @@
 | +0#0000e05#a8a8a8255@1| +0#0000000#ffffff0@3|{| @29||+1&&| +0#0000e05#a8a8a8255@1| +0#0000000#ffffff0@3|{| @29
 | +0#0000e05#a8a8a8255@1| +0#0000000#5fd7ff255@7|p|r|i|n|t|f|(|"|Y|o|u|r| |a|n|s|w|e|r| |i|s|:| |"|)|;||+1&#ffffff0| +0#0000e05#a8a8a8255@1|-+0#4040ff13#afffff255@34
 |X+3#0000000#ffffff0|f|i|l|e|1| @12|1|,|1| @11|T|o|p| |X+1&&|f|i|l|e|2| @12|1|,|1| @11|T|o|p
-|:+0&&|s|e|t| |d|i|f@1|o|p|t|+|=|a|l|g|o|r|i|t|h|m|:|p|a|t|i|e|n|c|e| @42
+|:+0&&|s|e|t| |d|i|f@1|o|p|t|+|=|a|l|g|o|r|i|t|h|m|:|h|i|s|t|o|g|r|a|m| @41
diff --git a/src/testdir/dumps/Test_diff_11.dump b/src/testdir/dumps/Test_diff_11.dump
index 0e4268e..3b24ebb 100644
--- a/src/testdir/dumps/Test_diff_11.dump
+++ b/src/testdir/dumps/Test_diff_11.dump
@@ -17,4 +17,4 @@
 | +0#0000e05#a8a8a8255@1|~+0#4040ff13#ffffff0| @33||+1#0000000&| +0#0000e05#a8a8a8255@1|~+0#4040ff13#ffffff0| @33
 | +0#0000e05#a8a8a8255@1|~+0#4040ff13#ffffff0| @33||+1#0000000&| +0#0000e05#a8a8a8255@1|~+0#4040ff13#ffffff0| @33
 |X+3#0000000&|f|i|l|e|1| @12|1|,|0|-|1| @9|A|l@1| |X+1&&|f|i|l|e|2| @12|1|,|0|-|1| @9|A|l@1
-|:+0&&|s|e|t| |d|i|f@1|o|p|t|+|=|i|n|d|e|n|t|-|h|e|u|r|i|s|t|i|c| @44
+|:+0&&| @73
diff --git a/src/testdir/screendump.vim b/src/testdir/screendump.vim
index 1b74c1b..139f708 100644
--- a/src/testdir/screendump.vim
+++ b/src/testdir/screendump.vim
@@ -103,6 +103,8 @@
 
   let i = 0
   while 1
+    " leave some time for updating the original window
+    sleep 10m
     call delete(testfile)
     call term_dumpwrite(a:buf, testfile, a:options)
     if readfile(reference) == readfile(testfile)
@@ -113,12 +115,11 @@
       " Leave the test file around for inspection.
       let msg = 'See dump file difference: call term_dumpdiff("' . testfile . '", "' . reference . '")'
       if a:0 == 1
-	let msg = a:1 . ': ' . msg
+        let msg = a:1 . ': ' . msg
       endif
       call assert_report(msg)
       return 1
     endif
-    sleep 10m
     let i += 1
   endwhile
   return 0
diff --git a/src/testdir/test_diffmode.vim b/src/testdir/test_diffmode.vim
index 4f20395..84fb451 100644
--- a/src/testdir/test_diffmode.vim
+++ b/src/testdir/test_diffmode.vim
@@ -813,8 +813,16 @@
   call term_sendkeys(buf, ":set diffopt+=internal\<cr>")
   call VerifyScreenDump(buf, 'Test_diff_10', {})
 
-  call term_sendkeys(buf, ":set diffopt+=indent-heuristic\<cr>")
-  call VerifyScreenDump(buf, 'Test_diff_11', {})
+  " Leave trailing : at commandline!
+  call term_sendkeys(buf, ":set diffopt+=indent-heuristic\<cr>:\<cr>")
+  call VerifyScreenDump(buf, 'Test_diff_11', {}, 'one')
+  " shouldn't matter, if indent-algorithm comes before or after the algorithm
+  call term_sendkeys(buf, ":set diffopt&\<cr>")
+  call term_sendkeys(buf, ":set diffopt+=indent-heuristic,algorithm:patience\<cr>:\<cr>")
+  call VerifyScreenDump(buf, 'Test_diff_11', {}, 'two')
+  call term_sendkeys(buf, ":set diffopt&\<cr>")
+  call term_sendkeys(buf, ":set diffopt+=algorithm:patience,indent-heuristic\<cr>:\<cr>")
+  call VerifyScreenDump(buf, 'Test_diff_11', {}, 'three')
 
   " Test 12: diff the same file
   call WriteDiffFiles(buf, [1, 2, 3, 4, 5, 6, 7, 8, 9, 10], [1, 2, 3, 4, 5, 6, 7, 8, 9, 10])