acid: source: Return null hash on error

This seems like a more consistent behavior.  Also, I would like to embed
the git hash into the build log record somehow.  Returning all zeroes in
an error case allows the main script to simply pass along the result
instead of worrying about an edge case.

Signed-off-by: Malfurious <m@lfurio.us>

2 files changed, 12 insertions, 6 deletions

diff --git a/acid/acid b/acid/acid
index 4f4da5a..d75e475 100755
--- a/acid/acid
+++ b/acid/acid
@@ -7,6 +7,7 @@
 CYCHE_SERVICE_DIR="/data/services"
 CYCHE_LOG_DIR="/data/logs"
 CYCHE_STATUS_FILE="/data/status"
+NULL_HASH="0000000000000000000000000000000000000000"
 source config.sh
 
 now() {
diff --git a/acid/acid-source b/acid/acid-source
index 29b1516..351d3d0 100755
--- a/acid/acid-source
+++ b/acid/acid-source
@@ -12,8 +12,8 @@
 # The caller should cache this hash value upon successful deployment.
 #
 # If a new version of the file tree is checked out, this file exits with code 1,
-# otherwise a stale success exits with 0.  On any error, no hash is printed, and
-# we exit with 2.
+# otherwise a stale success exits with 0.  On any error, the null hash is
+# printed, and we exit with 2.
 
 gethash() {
     git for-each-ref \
@@ -23,16 +23,21 @@ gethash() {
         "$1" # pattern
 }
 
+fail() {
+    echo "$NULL_HASH"
+    exit 2
+}
+
 cd "$CYCHE_SERVICE_DIR"
 
 # For <name>, limit to a-z, 0-9, -, _
 if ! echo "$1" | grep -Eq '^[-_a-z0-9]*$'; then
     echo "Bad service name: $1" >&2
-    exit 2
+    fail
 fi
 
 if ! [ -d "$1" ]; then
-    git clone "$2" "$1" >&2 || exit 2
+    git clone "$2" "$1" >&2 || fail
     touch "$1/.git/previous_hash"
     touch "$1/.git/previous_slug"
 fi
@@ -40,14 +45,14 @@ fi
 cd "$1"
 
 git remote set-url origin "$2" >&2 # pick up url changes
-git fetch --all --prune >&2 || exit 2
+git fetch --all --prune >&2 || fail
 
 prev=$(cat '.git/previous_hash')
 next=$(gethash "$3")
 
 if [ -z "$next" ]; then
     echo "No refs match $3" >&2
-    exit 2
+    fail
 fi
 
 echo "$next"