Fix bigword bindings with single-character words

With a commandline like

```
a b c d
```

and the cursor at the beginning, this would eat "a b", which isn't a
sensible bigword.

Bigword should be "a word, with optional leading whitespace".

This was caused by an overly zealous state-machine that always ate one
char and only *then* started eating leading whitespace.

Instead eat *a character*, and if it was whitespace go on eating
whitespace, and if it was a printable go straight to only eating
printables.

Fixes #7325.

src/tokenizer.cpp

@@ -807,6 +807,7 @@ bool move_word_state_machine_t::consume_char_path_components(wchar_t c) {
 }
 
 bool move_word_state_machine_t::consume_char_whitespace(wchar_t c) {
+    // Consume a "word" of printable characters plus any leading whitespace.
     enum { s_always_one = 0, s_blank, s_graph, s_end };
 
     bool consumed = false;
@@ -814,7 +815,13 @@ bool move_word_state_machine_t::consume_char_whitespace(wchar_t c) {
         switch (state) {
             case s_always_one: {
                 consumed = true;  // always consume the first character
-                state = s_blank;
+                // If it's a graphical char, only consume those from here.
+                if (iswgraph(c)) {
+                    state = s_graph;
+                } else {
+                    // If it's whitespace, keep consuming whitespace until the graphs.
+                    state = s_blank;
+                }
                 break;
             }
             case s_blank: {

tests/pexpects/bind.py

@@ -276,3 +276,16 @@ sendline("bind q self-insert-notfirst")
 expect_prompt()
 sendline("qqqecho qqq")
 expect_prompt("qqq", unmatched="Leading qs not stripped")
+
+# Test bigword with single-character words.
+sendline("bind \cg kill-bigword")
+expect_prompt()
+send("a b c d\x01") # ctrl-a, move back to the beginning of the line
+send("\x07") # ctrl-g, kill bigword
+sendline("echo")
+expect_prompt("^b c d")
+
+send("    a b c d\x01") # ctrl-a, move back to the beginning of the line
+send("\x07") # ctrl-g, kill bigword
+sendline("echo")
+expect_prompt("^b c d")