Make the directory holding session files configurable

* cdlog.sh (cdlog_sess_dir): New variable.
(cdlog.init, cdlog.recover): Create the session directory, if
necessary.  Interpolate the variable into all the places where
we previously referenced the home directory ~.
In cdlog.recover print that directory so the user knows
where the sessions are coming from.

* README.md: Documented.

2 files changed, 29 insertions, 8 deletions

diff --git a/README.md b/README.md
index 46f5e3d..af0da43 100644
--- a/README.md
+++ b/README.md
@@ -157,6 +157,20 @@ the history.
 LRU mode keeps duplicate directories out of the history and while
 promoting recently used directories toward the top.
 
+## Alternative Session Directory
+
+By default, `cdlog` keeps the session recovery files in your home
+directory. They have numbered names like `.cdlog.1.dirs`.
+The variable `cdlog_sess_dir` may be assigned a directory path
+to specify an alternative directory. This path should omit the
+trailing slash. If the variable is empty, it denotes the
+root directory. If the directory doesn't exist, `cdlog` will try
+to create it. The main use for this configuration is to support
+the situation when a home directory is shared among multiple
+host machines with different environments. You can interpolate the
+value of `$HOSTNAME` into `cdlog_sess_dir` to have sessions specific
+to a host.
+
 ## Completion
 
 `cdlog` provides its own Tab completion for the `cd` command, overriding
diff --git a/cdlog.sh b/cdlog.sh
index 888a858..2e2fae9 100644
--- a/cdlog.sh
+++ b/cdlog.sh
@@ -11,6 +11,7 @@ unset cdlog_alias[0]              # history is 1-based
 
 # Configuration variables
 cdlog_lru=${cdlog_lru-}
+cdlog_sess_dir=${cdlog_sess_dir-~}
 
 # Set state from args
 cdlog.args()
@@ -53,8 +54,11 @@ cdlog.init()
   local i
   local oldest
   local context
+  local csd=$cdlog_sess_dir
   declare -n d=cdlog_hist
 
+  mkdir -p "$csd"
+
   for ((i = 0; i < ${#d[@]}; i++)); do
     unset d[$i]
   done
@@ -63,7 +67,7 @@ cdlog.init()
   context=
 
   for i in {1..10}; do
-    if ! [ -f ~/.cdlog.$i.dirs ] ; then
+    if ! [ -f "$csd"/.cdlog.$i.dirs ] ; then
       context=$i
       break
     fi
@@ -72,19 +76,19 @@ cdlog.init()
   if ! [ $context ] ; then
     oldest=1
     for i in {2..10}; do
-      if [ ~/.cdlog.$i.dirs -ot ~/.cdlog.$oldest.dirs ] ; then
+      if [ "$csd"/.cdlog.$i.dirs -ot "$csd"/.cdlog.$oldest.dirs ] ; then
         oldest=$i
       fi
     done
     context=$oldest
   fi
 
-  cdlog_dirs=~/.cdlog.$context.dirs
+  cdlog_dirs="$csd"/.cdlog.$context.dirs
   cdlog_new_dirs=$cdlog_dirs
   rm -f $cdlog_dirs
 
-  set -- ~/.cdlog.*.dirs
-  if [ $# -gt 0 -a $1 != ~/.cdlog.'*'.dirs ] ; then
+  set -- "$csd"/.cdlog.*.dirs
+  if [ $# -gt 0 -a $1 != "$csd"/.cdlog.'*'.dirs ] ; then
     printf "Use 'cdr' or 'cdlog.recover' to switch to prior cdlog context.\n"
   fi
 
@@ -97,11 +101,14 @@ cdlog.recover()
   local dirs
   local i
   local sel
+  local csd=$cdlog_sess_dir
+
+  mkdir -p "$csd"
 
-  set -- ~/.cdlog.*.dirs
+  set -- "$csd"/.cdlog.*.dirs
 
-  if [ $# -gt 0 -a $1 != ~/.cdlog.'*'.dirs ] ; then
-    printf "These cdlog contexts exist:\n"
+  if [ $# -gt 0 -a $1 != "$csd"/.cdlog.'*'.dirs ] ; then
+    printf "These cdlog contexts exist in %s:\n" "$csd"
     i=0
     for dirs in "$@"; do
       printf "[%d]: %s%s\n" $((++i)) \