fish_clipboard_paste: trim indentation when pasting multiple lines

When pasting a multiline command with indented blocks, extra indentation
from spaces, or tabs, is generally undesirable, because fish already indents
pipes and blocks. Discard the indentation unless the cursor or the pasted
part is inside quotes.

Users who copied fish_clipboard_paste need to update it because
__fish_commandline_is_singlequoted had an API change and was renamed.

CHANGELOG.rst

@@ -278,6 +278,7 @@ New or improved bindings
 -  As mentioned above, new special input functions ``undo`` (Control+\_ or Control+Z) and ``redo`` (Alt-/) can be used to revert changes to the command line or the pager search field (:issue:`6570`).
 -  Control-Z is now available for binding (:issue:`7152`).
 -  Additionally, using the ``cancel`` special input function (bound to escape by default) right after fish picked an unambiguous completion will undo that (:issue:`7433`).
+- ``fish_clipboard_paste`` (Control+V) trims indentation from multiline commands because fish already indents (:issue:`7662`).
 -  Vi mode bindings now support ``dh``, ``dl``, ``c0``, ``cf``, ``ct``, ``cF``, ``cT``, ``ch``, ``cl``, ``y0``, ``ci``, ``ca``, ``yi``, ``ya``, ``di``, ``da``, ``d;``, ``d,``, ``o``, ``O`` and Control+left/right keys to navigate by word (:issue:`6648`, :issue:`6755`, :issue:`6769`, :issue:`7442`, :issue:`7516`).
 -  Vi mode bindings support ``~`` (tilde) to toggle the case of the selected character (:issue:`6908`).
 -  Functions ``up-or-search`` and ``down-or-search`` (up-arrow and down-arrow) can cross empty lines and don't activate search mode if the search fails which makes it easier to use them to move between lines in some situations.

share/functions/__fish_tokenizer_state.fish

@@ -1,4 +1,4 @@
-function __fish_commandline_is_singlequoted --description "Return 0 if the current token has an open single-quote"
+function __fish_tokenizer_state --description "Print the state of the tokenizer at the end of the given string"
     # Go through the token char-by-char in a state machine.
     # The states are:
     # - normal - no quoting is active (the starting state)
@@ -8,8 +8,15 @@ function __fish_commandline_is_singlequoted --description "Return 0 if the curre
     # - single-escaped - open \\ inside single-quotes
     # - double-escaped - open \\ inside double-quotes
 
+    argparse --min-args 1 --max-args 1 i/initial-state= -- $argv
+    or return 1
+
     set -l state normal
-    for char in (commandline -ct | string split "")
+    if set -q _flag_initial_state
+        set str $_flag_initial_state
+    end
+
+    for char in (string split -- "" $argv[1])
         switch $char
             case "'" # single-quote
                 switch $state
@@ -51,10 +58,6 @@ function __fish_commandline_is_singlequoted --description "Return 0 if the curre
                 end
         end
     end
-    # TODO: Should "single-escaped" also be a success?
-    if contains -- $state single single-escaped
-        return 0
-    else
-        return 1
-    end
+
+    echo $state
 end

share/functions/fish_clipboard_paste.fish

@@ -26,12 +26,28 @@ function fish_clipboard_paste
     # in order to turn it into a single literal token.
     #
     # This eases pasting non-code (e.g. markdown or git commitishes).
-    if __fish_commandline_is_singlequoted
+    set -l quote_state (__fish_tokenizer_state -- (commandline -ct))
+    if contains -- $quote_state single single-escaped
         if status test-feature regex-easyesc
             set data (string replace -ra "(['\\\])" '\\\\$1' -- $data)
         else
             set data (string replace -ra "(['\\\])" '\\\\\\\$1' -- $data)
         end
+    else if not contains -- $quote_state double double-escaped
+        and set -q data[2]
+        # Leading whitespace in subsequent lines is unneded, since fish
+        # already indents. Also gets rid of tabs (issue #5274).
+        set -l tmp
+        for line in $data
+            switch $quote_state
+                case normal
+                    set -a tmp (string trim -l -- $line)
+                case single single-escaped double double-escaped escaped
+                    set -a tmp $line
+            end
+            set quote_state (__fish_tokenizer_state -i $quote_state -- $line)
+        end
+        set data $data[1] $tmp[2..]
     end
     if not string length -q -- (commandline -c)
         # If we're at the beginning of the first line, trim whitespace from the start,