New feature: auto recovery.

* README.md: Describe the cdlog_autorecovery variable.

* cdlog.sh (cdlog_autorecover): New variable.
(cdlog.init): When there is only one saved session, then
call cdlog.recover with the secret new __auto argument.
(cdlog.recover): When there is only one saved session
and the __auto argument has been given, then make the
selection 1 for the user. In this case we print the
current working directory.

2 files changed, 42 insertions, 4 deletions

diff --git a/README.md b/README.md
index 5382ddb..4857d22 100644
--- a/README.md
+++ b/README.md
@@ -140,7 +140,7 @@ stamp and chooses its index.
 
 When one or more persisted session are present, `cdlog`'s initialization
 mentions this, suggesting that the `cdr` command may be used to recover
-to one of the sessions.
+to one of the sessions. See also the Auto Recovery section below.
 
 ## LRU Mode
 
@@ -157,6 +157,9 @@ directory, and is removed; the entries above it shift down to take
 its place, and the previous current directory becomes the top of
 the history.
 
+LRU mode is disabled when the `cdlog_lru` variable is empty,
+which is its initial value.
+
 LRU mode keeps duplicate directories out of the history and while
 promoting recently used directories toward the top.
 
@@ -174,6 +177,25 @@ host machines with different environments. You can interpolate the
 value of `$HOSTNAME` into `cdlog_sess_dir` to have sessions specific
 to a host.
 
+## Auto Recovery
+
+When the `cdlog_autorecover` variable is set to `y`, `cdlog` will
+automatically recover the session without the need for using the
+`cdr` command. This only happens when these two conditions hold:
+
+1. Bash is either a login shell, or the `SHLVL` variable is `1`.
+
+2. There is only one saved session.
+
+This feature exists because it is extremely common to use `cdr`
+upon logging in and to choose the only available session, by
+selecting `1`. However, automatic recovery may navigate away from
+the home directory, which may surprise the user who has not logged
+into that host in a long time. Thus it is not default behavior.
+
+When `cdlog_autorecover` is empty, which is the initial value,
+the feature is disabled.
+
 ## Completion
 
 `cdlog` provides its own Tab completion for the `cd` command, overriding
diff --git a/cdlog.sh b/cdlog.sh
index 2e2fae9..4a3b92b 100644
--- a/cdlog.sh
+++ b/cdlog.sh
@@ -12,6 +12,7 @@ unset cdlog_alias[0]              # history is 1-based
 # Configuration variables
 cdlog_lru=${cdlog_lru-}
 cdlog_sess_dir=${cdlog_sess_dir-~}
+cdlog_autorecover=${cdlog_autorecover-}
 
 # Set state from args
 cdlog.args()
@@ -89,7 +90,13 @@ cdlog.init()
 
   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"
+    if [ "$cdlog_autorecover" -a $# -eq 1 -a \
+          \( "$SHLVL" == 1 -o "${0%%[a-z]*}" == "-" \) ]
+    then
+      cdlog.recover __auto
+    else
+      printf "Use 'cdr' or 'cdlog.recover' to switch to prior cdlog context.\n"
+    fi
   fi
 
   # Also init var nicknames, but don't save context
@@ -102,12 +109,19 @@ cdlog.recover()
   local i
   local sel
   local csd=$cdlog_sess_dir
+  local auto=$1
+  local print=
 
   mkdir -p "$csd"
 
   set -- "$csd"/.cdlog.*.dirs
-
-  if [ $# -gt 0 -a $1 != "$csd"/.cdlog.'*'.dirs ] ; then
+  if [ $# -eq 1 -a $1 == "$csd"/.cdlog.'*'.dirs ] ; then
+    : # nothing
+  elif [ $# -eq 1 -a "$auto" == __auto ] ; then
+    printf "Auto-recovering cdlog session 1.\n"
+    cdlog_dirs=$(cdlog.get_param 1 "$@")
+    print=y
+  else
     printf "These cdlog contexts exist in %s:\n" "$csd"
     i=0
     for dirs in "$@"; do
@@ -166,6 +180,8 @@ cdlog.recover()
     unset cdlog_hist[0]
     cdlog.update
   fi
+
+  [ $print ] && printf "%s\n" "$PWD"
 }
 
 # Resolve @ search item to number