watchbot: Add repository monitoring script

This commit adds a script that can be used to monitor local repositories
for changes, and add them to a work queue when they need to be rebuilt.

diff --git a/watchbot.sh b/watchbot.sh
new file mode 100755 (executable)
index 0000000..59d39ea
--- /dev/null
+++ b/watchbot.sh
@@ -0,0 +1,188 @@
+#!/bin/bash
+
+sem="watchbot"
+
+watch_repos() {
+       local queue="$1"
+       local watches=("${@:2}")
+
+       local nwatches
+       local heads
+       local i
+
+       heads=()
+       nwatches="${#watches[@]}"
+
+       if ! sem_init "$sem" 0; then
+               log_info "Another instance is already running"
+               return 1
+       fi
+
+       for (( i = 0; i < nwatches; i++ )); do
+               heads["$i"]=$(<"${watches[$i]}")
+       done
+
+       while ! sem_trywait "$sem"; do
+               log_debug "Watching $nwatches files: ${watches[@]}"
+               if ! inotifywait -qq -t 15 "${watches[@]}"; then
+                       continue
+               fi
+
+               for (( i = 0; i < nwatches; i++ )); do
+                       local cur_head
+
+                       cur_head=$(<"${watches[$i]}")
+
+                       log_debug "${watches[$i]}: ${heads[$i]} -> $cur_head"
+
+                       if [[ "$cur_head" != "${heads[$i]}" ]]; then
+                               if ! queue_put "$queue" "${watches[$i]}"; then
+                                       log_error "Could not place item in queue"
+                                       continue
+                               fi
+
+                               heads["$i"]="$cur_head"
+                       fi
+               done
+       done
+
+       if ! sem_destroy "$sem"; then
+               log_error "Could not clean up semaphore $sem"
+       fi
+
+       return 0
+}
+
+stop() {
+       if ! sem_post "$sem"; then
+               log_info "Looks like no instances are running"
+               return 1
+       fi
+
+       return 0
+}
+
+watchlist_add() {
+       local opt="$1"
+       local repo="$2"
+
+       watchlist+=("$repo")
+       return 0
+}
+
+watch_to_head() {
+       local watch="$1"
+
+       local repo
+       local branch
+       local head
+
+       if [[ "$watch" == *"#"* ]]; then
+               repo="${watch%#*}"
+               branch="${watch##*#}"
+       else
+               repo="$watch"
+               branch="master"
+       fi
+
+       if [ -d "$repo/.git" ]; then
+               head="$repo/.git/refs/heads/$branch"
+       else
+               head="$repo/refs/heads/$branch"
+       fi
+
+       if ! [ -e "$head" ]; then
+               return 1
+       fi
+
+       log_debug "Resolved $watch to $head"
+
+       echo "$head"
+       return 0
+}
+
+verbosity_increase() {
+       local verbosity
+
+       verbosity=$(log_get_verbosity)
+       ((verbosity++))
+       log_set_verbosity "$verbosity"
+       return 0
+}
+
+verbosity_decrease() {
+       local verbosity
+
+       verbosity=$(log_get_verbosity)
+       ((verbosity--))
+       log_set_verbosity "$verbosity"
+       return 0
+}
+
+main() {
+       declare -ag watchlist # will be gone once forked to the background
+       local watches
+       local queue
+       local watch
+
+       opt_add_arg "r" "repo"    "yes" "" "Repository to watch (format: /repo/path[#branch])" watchlist_add
+       opt_add_arg "q" "queue"   "yes" "" "Queue used to distribute work"
+       opt_add_arg "s" "stop"    "no"  0  "Stop a running instance"
+       opt_add_arg "v" "verbose" "no"  0  "Be more verbose"                                   verbosity_increase
+       opt_add_arg "w" "shush"   "no"  0  "Be less verbose"                                   verbosity_decrease
+
+       if ! opt_parse "$@"; then
+               return 1
+       fi
+
+       if (( $(opt_get "stop") > 0 )); then
+               if ! stop; then
+                       return 1
+               fi
+
+               return 0
+       fi
+
+       queue=$(opt_get "queue")
+
+       if [ -z "$queue" ]; then
+               log_error "Need a queue"
+               return 1
+       fi
+
+       watches=()
+
+       for watch in "${watchlist[@]}"; do
+               local head
+
+               if ! head=$(watch_to_head "$watch"); then
+                       log_error "Cannot resolve $watch"
+                       return 1
+               fi
+
+               watches+=("$head")
+       done
+
+       if (( ${#watches[@]} == 0 )); then
+               log_error "Nothing to watch"
+               return 1
+       fi
+
+       start "$queue" "${watches[@]}" </dev/null &>/dev/null &
+       disown
+
+       return 0
+}
+
+{
+       if ! . toolbox.sh; then
+               exit 1
+       fi
+
+       if ! include "log" "opt" "sem" "queue"; then
+               exit 1
+       fi
+
+       main "$@"
+       exit "$?"
+}