added <FG> command and special Q-Register "$" to set and get the current working directory

 * FG stands for "Folder Go"
 * FG behaves similar to a Unix shell `cd`.
   Without arguments, it changes to the $HOME directory.
 * The $HOME directory was previously only used by $SCITECOCONFIG on Unix.
   Now it is documented on its own, since the HOME directory should also
   be configurable on Windows - e.g. to adapt SciTECO to a MinGW or Cygwin
   installation.
   HOME is initialized just like the other environment variables.
   This also means that now, the $HOME Q-Register is always defined
   and can be used by platform-agnostic macros.
 * FG uses a new kind of tab-completion: for directories only.
   It would be annoying to complete the FG command after every
   directory, so this tab-completion does not close the command
   automatically. Theoretically, it would be possible to close
   the command after completing a directory with no subdirectories,
   but this is not supported currently.
 * Filename arguments are no longer completed with " " if {} escaping
   is in place as this brings no benefit. Instead no completion character
   is inserted for this escape mode.
 * "$" was mapped to the current directory to support an elegant way to
   insert/get the current directory.
   Also this allows the idiom "[$ FG...new_dir...$ ]$" for changing
   the current directory temporarily.
 * The Q-Register stack was extended to support restoring the string
   part of special Q-Registers (that overwrite the default functionality)
   when using the "[$" and "]$" commands.
 * fixed minor typos (american spelling)

2 files changed, 44 insertions, 8 deletions

diff --git a/doc/sciteco.1.in b/doc/sciteco.1.in
index 3129189..0f091db 100644
--- a/doc/sciteco.1.in
+++ b/doc/sciteco.1.in
@@ -145,23 +145,32 @@ batch mode processing.
 .SH ENVIRONMENT
 .
 Before \*(ST executes any macro, all of the variables in the process
-environment are inserted into the global
-.I Q-Register
-table.
+environment are inserted into the global Q-Register table.
 A dollar sign is prepended before each variable name, so that for
 instance the variable \(lqHOME\(rq can be examined by macros by
 reading the string-content of Q-Register \(lq$HOME\(rq.
+Changes to these Q-Registers are currently not applied to
+the corresponding environment variables.
+.LP
 The following environment variables are initialized with default
 values by \*(ST if they are unset:
 .TP
+.B HOME
+Home directory of the current user.
+This may be used e.g. by the \fBFG\fP command.
+If unset, it defaults to the current user's home directory
+as set by
+.BR passwd (5)
+or as determined by other platform-dependent means.
+Initialization of this variable ensures that the
+\(lq$HOME\(rq Q-Register is available even on Windows
+and the home directory can always be re-configured.
+.TP
 .B SCITECOCONFIG
 Path where \*(ST looks for configuration files.
 For instance, this is the path of the default profile.
 If unset, this variable defaults to the \fBHOME\fP
-environment variable on UNIX/Linux.
-If \fBHOME\fP is unset, it defaults to the current user's
-home directory as set by
-.BR passwd (5).
+environment variable on Unix.
 On Windows, this variable defaults to the location of the
 \*(ST program executable, so that \*(ST is self-contained
 on Windows.
@@ -181,7 +190,7 @@ defaults to the standard library installation path at
 .BR "@scitecolibdir@" .
 .
 .LP
-Both the \fBSCITECOCONFIG\fP and \fBSCITECOPATH\fP environment
+The \fBHOME\fP, \fBSCITECOCONFIG\fP and \fBSCITECOPATH\fP environment
 variables are canonicalized to absolute paths.
 Therefore it is possible to define them relative to the
 working directory of \*(ST when it starts up while macros
diff --git a/doc/sciteco.7.template b/doc/sciteco.7.template
index 4fccd33..8272b08 100644
--- a/doc/sciteco.7.template
+++ b/doc/sciteco.7.template
@@ -443,6 +443,13 @@ Fully completed filenames terminate the string argument,
 except if the \(lq{\(rq terminator is used.
 T}
 T{
+Auto complete directory
+T};9;^I, Tab;T{
+Directory arguments
+T};T{
+Auto complete directory beginning at the start of the argument.
+T}
+T{
 Auto complete symbol
 T};9;^I, Tab;T{
 Scintilla symbol arguments
@@ -1022,6 +1029,26 @@ temporarily:
 [* ! ...change current buffer... ! ]*
 .EE
 .TP
+.BR $ " (dollar)"
+The process' current working directory (string part).
+Its numeric part is currently unused.
+The working directory will always be returned as an
+absolute path with normalized forward-slash directory
+separators.
+It is possible to set this register using the \fB^U\fP or
+\fBEU\fP commands which will change the current working
+directory in a manner similar to the \fBFG\fP command.
+This allows you to change the current directory temporarily
+with the following idiom:
+.EX
+[$ ! ...change current directory... ! ]$
+.EE
+As with \fBFG\fP, relative directories may be specified
+but querying \(lq$\(rq will still return an absolute path.
+The \(lq$\(rq register may also be edited but changing its
+string contents this way has no effect on the current
+working directory.
+.TP
 .BR $ " (Escape)"
 Command-line replacement register.
 Its integer part is unused.