merge fish histories in open shells

fish.configlink/functions/up-or-search.fish

@@ -0,0 +1,29 @@
+# by @farcaller from https://github.com/fish-shell/fish-shell/issues/825#issuecomment-440286038
+
+function up-or-search -d "Depending on cursor position and current mode, either search backward or move up one line"
+    # If we are already in search mode, continue
+    if commandline --search-mode
+        commandline -f history-search-backward
+        return
+    end
+
+    # If we are navigating the pager, then up always navigates
+    if commandline --paging-mode
+        commandline -f up-line
+        return
+    end
+
+    # We are not already in search mode.
+    # If we are on the top line, start search mode,
+    # otherwise move up
+    set lineno (commandline -L)
+
+    switch $lineno
+        case 1
+            commandline -f history-search-backward
+            history merge # <-- ADDED THIS
+
+        case '*'
+            commandline -f up-line
+    end
+end