It is impossible to rematch a pattern which has one (or both)
of these operators, so the simplest solucion is detect them
while we are compiling the regular expression and break the
match loop after the first iteration.
Ed was falling doing substitution different of the first or all
(s//%/, s//%/\1, s//%/g), because it was not adding the matches
which were not going to be substituted.
Rematch() was incremnenting the last match always, even in the
cases when it was not matching anything. This patch detects
this situation and it updates it only when there is a match.
Line 0 is a special line added to allow operations with
empty buffers, and we have to ensure that it is not going
to match any regular expression. The code was written in
a way that this case was handle implicitily, but this
solution was working only for the first file loaded in
ed, while the second file loaded in ed got a line with
a dirty seek field. This solution check explicitily
against invalid lines passed to makeline(), which
allows to simplify the common case.
The current behaviour of storing the scratch file in
the current directory is a bit painful, because it
generates files in all the directories where you
execute ed. BSD ed uses TMPDIR for this purpouse,
so if the user wants to put the scratch file in
other place different of /tmp it only has to set
this variable.
This patch introduced init() function, which removed the initialization
code of savfname in doread, but this is incorrect, because savfname
can be initialized with a r command if savfname is empty.
These funcction initializes the scratch buffer, and in case of
having a file name parameter it loads the file in the scratch.
It also fixes a problem before this version, where the saved
filename was not set when the file didn't exist.
For the same reason we don't care about the state of
the buffer in clearundo() we can reset modflag in
clearbuf(), because after calling it we don't want
to know anything about the previous state.
When we discard the content of an undo buffer
is because we don't need it anymore, and it means
that we don't care about the modify state of the buffer
so we can reset the modflag in clearundo(), and
remove this assignation each time clearundo() is called.
getrhs() must remove \ excepts in the case of & and \d
(where d is a digit), because in this case are sequences
understood by addsub(), so addsub() must be able to see
them.
When a error occurs it is important to remove all the modifications
done by the offending command and restore the value of dot to the
state before of executing the command.
