Add an additional {} syntax for defining strings in the configuration

file, making it much tidier to define commands that contain other tmux
or shell commands (like if-shell). Also tweak bind-key to expect a
string if it is only given one argument, so {} can be used with it as
well. From Avi Halachmi.

arguments.c

@@ -207,7 +207,7 @@ args_print(struct args *args)
 char *
 args_escape(const char *s)
 {
-	static const char	 quoted[] = " #\"';$";
+	static const char	 quoted[] = " #\"';${}";
 	char			*escaped, *result;
 	int			 flags;
 

cmd-bind-key.c

@@ -44,14 +44,16 @@ const struct cmd_entry cmd_bind_key_entry = {
 static enum cmd_retval
 cmd_bind_key_exec(struct cmd *self, struct cmdq_item *item)
 {
-	struct args		*args = self->args;
-	key_code		 key;
-	const char		*tablename;
-	struct cmd_parse_result	*pr;
+	struct args		 *args = self->args;
+	key_code		  key;
+	const char		 *tablename;
+	struct cmd_parse_result	 *pr;
+	char			**argv = args->argv;
+	int			  argc = args->argc;
 
-	key = key_string_lookup_string(args->argv[0]);
+	key = key_string_lookup_string(argv[0]);
 	if (key == KEYC_NONE || key == KEYC_UNKNOWN) {
-		cmdq_error(item, "unknown key: %s", args->argv[0]);
+		cmdq_error(item, "unknown key: %s", argv[0]);
 		return (CMD_RETURN_ERROR);
 	}
 
@@ -62,7 +64,10 @@ cmd_bind_key_exec(struct cmd *self, struct cmdq_item *item)
 	else
 		tablename = "prefix";
 
-	pr = cmd_parse_from_arguments(args->argc - 1, args->argv + 1, NULL);
+	if (argc == 2)
+		pr = cmd_parse_from_string(argv[1], NULL);
+	else
+		pr = cmd_parse_from_arguments(argc - 1, argv + 1, NULL);
 	switch (pr->status) {
 	case CMD_PARSE_EMPTY:
 		cmdq_error(item, "empty command");

cmd-parse.y

@@ -1236,6 +1236,99 @@ yylex_token_tilde(char **buf, size_t *len)
 	return (1);
 }
 
+static int
+yylex_token_brace(char **buf, size_t *len)
+{
+	struct cmd_parse_state	*ps = &parse_state;
+	int 			 ch, nesting = 1, escape = 0, quote = '\0';
+	int			 lines = 0;
+
+	/*
+	 * Extract a string up to the matching unquoted '}', including newlines
+	 * and handling nested braces.
+	 *
+	 * To detect the final and intermediate braces which affect the nesting
+	 * depth, we scan the input as if it was a tmux config file, and ignore
+	 * braces which would be considered quoted, escaped, or in a comment.
+	 *
+	 * The result is verbatim copy of the input excluding the final brace.
+	 */
+
+	for (ch = yylex_getc1(); ch != EOF; ch = yylex_getc1()) {
+		yylex_append1(buf, len, ch);
+		if (ch == '\n')
+			lines++;
+
+		/*
+		 * If the previous character was a backslash (escape is set),
+		 * escape anything if unquoted or in double quotes, otherwise
+		 * escape only '\n' and '\\'.
+		 */
+		if (escape &&
+		    (quote == '\0' ||
+		    quote == '"' ||
+		    ch == '\n' ||
+		    ch == '\\')) {
+			escape = 0;
+			continue;
+		}
+
+		/*
+		 * The character is not escaped. If it is a backslash, set the
+		 * escape flag.
+		 */
+		if (ch == '\\') {
+			escape = 1;
+			continue;
+		}
+		escape = 0;
+
+		/* A newline always resets to unquoted. */
+		if (ch == '\n') {
+			quote = 0;
+			continue;
+		}
+
+		if (quote) {
+			/*
+			 * Inside quotes or comment. Check if this is the
+			 * closing quote.
+			 */
+			if (ch == quote && quote != '#')
+				quote = 0;
+		} else  {
+			/* Not inside quotes or comment. */
+			switch (ch) {
+			case '"':
+			case '\'':
+			case '#':
+				/* Beginning of quote or comment. */
+				quote = ch;
+				break;
+			case '{':
+				nesting++;
+				break;
+			case '}':
+				nesting--;
+				if (nesting == 0) {
+					(*len)--; /* remove closing } */
+					ps->input->line += lines;
+					return (1);
+				}
+				break;
+			}
+		}
+	}
+
+	/*
+	 * Update line count after error as reporting the opening line
+	 * is more useful than EOF.
+	 */
+	yyerror("unterminated brace string");
+	ps->input->line += lines;
+	return (0);
+}
+
 static char *
 yylex_token(int ch)
 {
@@ -1282,6 +1375,13 @@ yylex_token(int ch)
 				goto error;
 			goto skip;
 		}
+		if (ch == '{' && state == NONE) {
+			if (!yylex_token_brace(&buf, &len))
+				goto error;
+			goto skip;
+		}
+		if (ch == '}' && state == NONE)
+			goto error;  /* unmatched (matched ones were handled) */
 
 		/*
 		 * ' and " starts or end quotes (and is consumed).

key-bindings.c

@@ -242,8 +242,8 @@ key_bindings_init(void)
 		"bind w choose-tree -Zw",
 		"bind x confirm-before -p\"kill-pane #P? (y/n)\" kill-pane",
 		"bind z resize-pane -Z",
-		"bind { swap-pane -U",
-		"bind } swap-pane -D",
+		"bind '{' swap-pane -U",
+		"bind '}' swap-pane -D",
 		"bind '~' show-messages",
 		"bind PPage copy-mode -u",
 		"bind -r Up select-pane -U",
@@ -347,8 +347,8 @@ key_bindings_init(void)
 		"bind -Tcopy-mode M-r send -X middle-line",
 		"bind -Tcopy-mode M-v send -X page-up",
 		"bind -Tcopy-mode M-w send -X copy-selection-and-cancel",
-		"bind -Tcopy-mode M-{ send -X previous-paragraph",
-		"bind -Tcopy-mode M-} send -X next-paragraph",
+		"bind -Tcopy-mode 'M-{' send -X previous-paragraph",
+		"bind -Tcopy-mode 'M-}' send -X next-paragraph",
 		"bind -Tcopy-mode M-Up send -X halfpage-up",
 		"bind -Tcopy-mode M-Down send -X halfpage-down",
 		"bind -Tcopy-mode C-Up send -X scroll-up",
@@ -413,8 +413,8 @@ key_bindings_init(void)
 		"bind -Tcopy-mode-vi t command-prompt -1p'(jump to forward)' 'send -X jump-to-forward \"%%%\"'",
 		"bind -Tcopy-mode-vi v send -X rectangle-toggle",
 		"bind -Tcopy-mode-vi w send -X next-word",
-		"bind -Tcopy-mode-vi { send -X previous-paragraph",
-		"bind -Tcopy-mode-vi } send -X next-paragraph",
+		"bind -Tcopy-mode-vi '{' send -X previous-paragraph",
+		"bind -Tcopy-mode-vi '}' send -X next-paragraph",
 		"bind -Tcopy-mode-vi % send -X next-matching-bracket",
 		"bind -Tcopy-mode-vi MouseDown1Pane select-pane",
 		"bind -Tcopy-mode-vi MouseDrag1Pane select-pane\\; send -X begin-selection",

tmux.1

@@ -490,11 +490,13 @@ line (the \e and the newline are completely removed).
 This is called line continuation and applies both inside and outside quoted
 strings and in comments.
 .Pp
-Command arguments may be specified as strings surrounded by either single (')
-or double quotes (").
+Command arguments may be specified as strings surrounded by single (') quotes,
+double quotes (") or braces ({}).
 .\" "
 This is required when the argument contains any special character.
-Strings cannot span multiple lines except with line continuation.
+Single and double quoted strings cannot span multiple lines except with line
+continuation.
+Braces can span multiple lines.
 .Pp
 Outside of quotes and inside double quotes, these replacements are performed:
 .Bl -dash -offset indent
@@ -520,6 +522,34 @@ is removed) and are not treated as having any special meaning - so for example
 variable.
 .El
 .Pp
+Braces are similar to single quotes in that the text inside is taken literally
+without replacements, but they can span multiple lines.
+They are designed to avoid the need for additional escaping when passing a group
+of
+.Nm
+or shell commands as an argument (for example to
+.Ic if-shell
+or
+.Ic pipe-pane ) .
+These two examples produce an identical command - note that no escaping is
+needed when using {}:
+.Bd -literal -offset indent
+if-shell true {
+    display -p 'brace-dollar-foo: }$foo'
+}
+
+if-shell true "\en    display -p 'brace-dollar-foo: }\e$foo'\en"
+.Ed
+.Pp
+Braces may be enclosed inside braces, for example:
+.Bd -literal -offset indent
+bind x if-shell "true" {
+    if-shell "true" {
+         display "true!"
+    }
+}
+.Ed
+.Pp
 Environment variables may be set by using the syntax
 .Ql name=value ,
 for example
@@ -820,15 +850,16 @@ directly without invoking the shell.
 .Op Ar arguments
 refers to a
 .Nm
-command, passed with the command and arguments separately, for example:
+command, either passed with the command and arguments separately, for example:
 .Bd -literal -offset indent
 bind-key F1 set-option status off
 .Ed
 .Pp
-Or if using
-.Xr sh 1 :
+Or passed as a single string argument in
+.Pa .tmux.conf ,
+for example:
 .Bd -literal -offset indent
-$ tmux bind-key F1 set-option status off
+bind-key F1 { set-option status off }
 .Ed
 .Pp
 Example