Initial version with Makefile and README

1 files changed, 72 insertions, 0 deletions

diff --git a/watch-git-tags b/watch-git-tags
new file mode 100755
index 0000000..ccccd00
--- /dev/null
+++ b/watch-git-tags
@@ -0,0 +1,72 @@
+#!/bin/sh
+self=watch-git-tags
+
+# List sorted local tags
+lt() {
+    git tag -l |
+        LC_COLLATE=C sort
+}
+
+# List sorted remote tags
+rt() {
+    git ls-remote -qt |
+        awk '!/\^\{\}$/{print substr($2,11)}' |
+        LC_COLLATE=C sort
+}
+
+# Create a temporary directory with name in $td, and handle POSIX-ish traps to
+# remove it when the script exits; requires mktemp(1) (not POSIX)
+td=$(mktemp -d) || exit
+cleanup() {
+    [ -n "$td" ] || return
+    rm -fr -- "$td"
+}
+for sig in EXIT HUP INT TERM ; do
+    # shellcheck disable=SC2064
+    trap "cleanup $sig" "$sig"
+done
+
+# Use current directory if no other arguments
+[ "$#" -gt 0 ] || set -- .
+
+# Iterate through each repo in a subshell in parallel
+for repo ; do (
+
+    # Make a temporary directory with a hash in its name for uniqueness
+    df=$(printf %s "$repo" | sed s:/:_:g)
+    cs=$(printf %s "$repo" | cksum)
+    sd=$td/$df.${cs%% *}
+    mkdir -- "$sd" || exit
+
+    # Step in and write repo path to file
+    cd -- "$sd" || exit
+    printf '%s\n' "$repo" > path || exit
+
+    # Write local and remote tags to files
+    (
+        cd -- "$repo" || exit
+        lt "$repo" > "$sd"/a || exit
+        rt "$repo" > "$sd"/b
+    ) ||
+    exit
+
+    # Write new tags to file
+    LC_COLLATE=C comm -13 -- [ab] > new
+
+) & done
+
+# Wait for each of those to finish
+wait
+
+# Iterate through the temp dirs in order
+for dir in "$td"/* ; do (
+    cd -- "$dir" || exit 0
+
+    # Look for non-zero "new" files (at least one new tag)
+    [ -s new ] || exit 0
+
+    # Print repository path and new tags
+    sed '1!s/^/\t/' -- path new
+    exit 1
+
+) ; done