add subshells, here-documents and redirections/pipes for control structures

- control structures can have redirections (while read l; do ...; done
  < file), which apply to all commands in them; they run in the shell
- in pipes and in the background they run in a subshell (cmd | while
  read l; do ...; done, for ...; done &, a && b &)
- ( list ) subshells; ( and ) are operators now
- here-documents <<EOF, <<-EOF, <<'EOF' and here-strings <<<word
- redirections of source apply to the commands of the file
- fix non-ASCII characters in quotes being mangled ('für')

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

packaging/man/gosh.1

@@ -320,6 +320,24 @@ Redirect standard output to where standard error goes.
 .BR &> " \fIfile\fP, " &>> " \fIfile\fP"
 Write (or append) standard output and standard error to
 .IR file .
+.TP
+.BI << word
+Here-document: the lines after the command, up to a line that is exactly
+.IR word ,
+are standard input. If no part of
+.I word
+is quoted, variables, command substitutions and backslashes before
+.BR $ ,
+.BR \(ga ,
+.B \e
+and newline are expanded in the lines.
+.BI <<\- word
+also removes leading tabs from the lines and the delimiter line.
+.TP
+.BI <<< " word"
+Here-string:
+.I word
+and a newline are standard input.
 .PP
 Redirections are evaluated from left to right. Only file descriptors 0, 1
 and 2 are supported.
@@ -331,6 +349,7 @@ and 2 are supported.
 \fBuntil\fP \fIlist\fP; \fBdo\fP \fIlist\fP; \fBdone\fP
 \fBcase\fP \fIword\fP \fBin\fP [\fB(\fP]\fIpattern\fP[\fB|\fP\fIpattern\fP]...\fB)\fP \fIlist\fP \fB;;\fP ... \fBesac\fP
 \fB{\fP \fIlist\fP; \fB}\fP
+\fB(\fP \fIlist\fP \fB)\fP
 \fB!\fP \fIcommand\fP
 .fi
 .PP
@@ -362,11 +381,23 @@ of the last clause may be omitted.
 .IR list ;
 .B }
 groups commands; they run in the current shell.
+.B (
+.I list
+.B )
+runs the commands in a subshell, a new
+.B gosh
+process, so that changes of the directory, variables and functions only
+apply there.
 .PP
-Control structures cannot be used in pipes, with redirections or in the
-background, and there are no
-.B ( ... )
-subshells.
+Redirections after a control structure
+.RB ( "done < file" ,
+.BR "fi > log 2>&1" )
+apply to all commands in it, which still run in the current shell. In a
+pipe and in the background
+.RB ( & ),
+a control structure runs in a subshell, like in
+.BR sh (1).
+The subshell knows the functions and positional parameters of the shell.
 .SS Functions
 .nf
 \fIname\fP\fB() {\fP \fIlist\fP; \fB}\fP
@@ -631,6 +662,9 @@ make > build.log 2>&1 || echo "failed: $?"
 LANG=C sort file
 alias ll=\(aqls \-l\(aq
 greet() { echo "Hello ${1:\-World}"; }
+git ls\-files | while read \-r f; do wc \-l "$f"; done
+while read \-r user rest; do echo "$user"; done < /etc/passwd
+(cd build && make) > build.log 2>&1
 case "$1" in start|stop) echo "$1ing" ;; *) echo "usage: $0 start|stop" ;; esac
 read \-r \-p \(aqName? \(aq name
 chsh \-s /usr/bin/gosh