Support multiple source directories

The `rcup` and `mkrc` commands now support multiple source directories.
This is useful for sharing dotfiles between friends, spliting dotfiles
into private and public ones, or other such situations.

In `mkrc` this support means that you can specify the destination
directory for your dotfile, either from the command-line or from you
`~/.rcrc` configuration.

In `rcup` this means that it will recur through all source directories,
in order, creating the symlinks as needed. This means that duplicated
files will not be overridden. The order can be specified by the `-d`
option, which can be repeated, or by the `DOTFILES_DIRS` option in your
`~/.rcrc` configuration. The `-d` option overrides the configuration.

For example, this configuration file will update from the two
directories in order:

    DOTFILES_DIRS="/home/mike/.dotfiles/public /home/mike/.dotfiles/private"

Any source directories that don't exist are skipped.

3 files changed, 21 insertions, 5 deletions

diff --git a/man/man1/mkrc.1 b/man/man1/mkrc.1
index 37a25b9..b241e6b 100644
--- a/man/man1/mkrc.1
+++ b/man/man1/mkrc.1
@@ -4,12 +4,13 @@
 mkrc \- bless files into a dotfile
 
 .SH SYNOPSIS
-.B mkrc [-v] [-q] [-t \fItag\fR] \fIfiles...\fR
+.B mkrc [-v] [-q] [-t \fItag\fR] [-d \fIdir\fR] \fIfiles...\fR
 
 .SH DESCRIPTION
 
 This program adds files to your dotfiles directory then installs it
-back into your home directory. It can install files under a tag.
+back into your home directory. It can install files under a tag or
+different source directory.
 
 It supports these options:
 
@@ -25,6 +26,11 @@ decrease verbosity
 \fB-t\fR \fITAG\fR
 install dotfiles according to tag
 
+.TP
+\fB-d\fR \fIDIR\fR
+install dotfiles under the specified directory. This can be specified
+multiple times.
+
 .SH AUTHOR
 
 Written by Mike Burns.
diff --git a/man/man1/rcup.1 b/man/man1/rcup.1
index a558b20..f68cc87 100644
--- a/man/man1/rcup.1
+++ b/man/man1/rcup.1
@@ -4,13 +4,13 @@
 rcup \- update and install dotfiles
 
 .SH SYNOPSIS
-.B rcup [-v] [-q] [-t \fItag\fR] [\fIfiles...\fR]
+.B rcup [-v] [-q] [-t \fItag\fR] [-d \fIdir\fR] [\fIfiles...\fR]
 
 .SH DESCRIPTION
 
 This is a program to update and install personal dotfiles. These
 dotfiles are managed in a separate directory. Use \fBrcup\fR to install
-files from your dotfiles directory or from host- or tag-specific
+files from your dotfiles directories or from host- or tag-specific
 directories within.
 
 See \fBDIRECTORY LAYOUT\fR for details on the directory layout.
@@ -27,7 +27,11 @@ decrease verbosity
 
 .TP
 \fB-t\fR \fITAG\fR
-install dotfiles according to tag
+install dotfiles according to TAG
+
+.TP
+\fB-d\fR \fIDIR\fR
+install dotfiles from the DIR. This can be specified multiple times.
 
 .TP
 \fIfiles...\fR
diff --git a/man/man5/rcrc.5 b/man/man5/rcrc.5
index 1032504..67dc2a3 100644
--- a/man/man5/rcrc.5
+++ b/man/man5/rcrc.5
@@ -16,9 +16,15 @@ It supports these variables:
 \fBTAGS\fR
 the default tags used by \fBrcup\fR\|.
 
+.TP
+\fBDOTFILES_DIRS\fR
+the source directories for dotfiles. The first in the list is the
+canonical source. The default value is \fI~/.dotfiles\fR\|.
+
 .SH EXAMPLES
 
 \&\fBTAGS="freebsd development email git laptop gmail notmuch"\fR
+\&\fBDOTFILES_DIRS="/home/mike/.dotfiles /usr/share/dotfiles"\fR
 
 .SH AUTHOR