Merge pull request #70 from cweagans/hooks

Dropping changes to `yadm.md` and `CONTRIBUTORS`. These are built
programmatically during releases.

yadm

@@ -97,10 +97,14 @@ function main() {
       shift
     done
     [ ! -d "$YADM_WORK" ] && error_out "Work tree does not exist: [$YADM_WORK]"
+    invoke_hook "pre_$YADM_COMMAND"
     $YADM_COMMAND "${YADM_ARGS[@]}"
+    invoke_hook "post_$YADM_COMMAND"
   else
     #; any other commands are simply passed through to git
+    invoke_hook "pre_$1"
     git_command "$@"
+    invoke_hook "post_$1"
     retval="$?"
   fi
 
@@ -853,6 +857,16 @@ function error_out() {
 
 }
 
+#: ******  Hook handler  ******S
+function invoke_hook() {
+  hook_name=$1
+
+  if [[ -x "$YADM_DIR/hooks/$hook_name.sh" ]] ; then
+    debug "invoking hook: $hook_name"
+    $YADM_DIR/hooks/$hook_name.sh
+  fi
+}
+
 #; ****** Auto Functions ******
 
 function auto_alt() {

yadm.1

@@ -400,6 +400,21 @@ Override the HOSTNAME for the purpose of symlinking alternate files.
 .TP
 .B local.user
 Override the USER for the purpose of symlinking alternate files.
+.SH HOOKS
+.B yadm
+has the capability to execute scripts before or after any operation that
+.B yadm
+can perform. To utilize this functionality, create a directory to store the hook
+scripts at
+.BR $HOME/.yadm/hooks.
+Then, create scripts inside this directory for whatever operation you want to
+hook into. For instance, if you'd like a script to run after
+.B yadm pull,
+your hook script should be executable and located at
+.BR $HOME/.yadm/hooks/post_pull.sh.
+Any of the
+.B yadm
+subcommands can utilize this functionality.
 .SH ALTERNATES
 When managing a set of files across different systems, it can be useful to have
 an automated way of choosing an alternate version of a file for a different