Detect unsafe repos and skip them.

In april 2022 a vulnerability was found in git. See
https://github.blog/2022-04-12-git-security-vulnerability-announced/.
The implemented fix for git is to warn the user and to skip the repo.
The warning screws up our output, so we also detect and skip those repos
with our own message.

Author: fboender

Makefile

@@ -15,7 +15,8 @@ man: mgitstatus.1
 test:
 		# SC1117 Backslash is literal in...
 		# SC2059 Don't use variables in the printf format string. But we need to or colors won't work
-		shellcheck -e SC1117,SC2059 mgitstatus
+		# SC2012 Use find instead of ls, but we need to extract the user id of the .git dir
+		shellcheck -e SC1117,SC2059,SC2012 mgitstatus
 
 .PHONY: install
 install:

mgitstatus

@@ -147,6 +147,10 @@ C_NEEDS_COMMIT="$C_RED"
 C_NEEDS_UPSTREAM="$C_PURPLE"
 C_UNTRACKED="$C_CYAN"
 C_STASHES="$C_YELLOW"
+C_UNSAFE="$C_PURPLE"
+
+# Get current username so we can check .git dir ownership.
+ID="$(id -n -u)"
 
 # Find all .git dirs, up to DEPTH levels deep. If DEPTH is 0, the scan is
 # infinitely deep
@@ -164,6 +168,15 @@ for DIR in "${@:-"."}"; do
         GIT_DIR="$PROJ_DIR/.git"
         GIT_CONF="$PROJ_DIR/.git/config"
 
+        # Check if the repo is safe (https://github.blog/2022-04-12-git-security-vulnerability-announced/)
+        if [ -d "$GIT_DIR" ]; then
+            GIT_DIR_OWNER="$(ls -ld "$GIT_DIR" | awk 'NR==1 {print $3}')"
+            if [ "$ID" != "$GIT_DIR_OWNER" ]; then
+                printf "${PROJ_DIR}: ${C_UNSAFE}Unsafe ownership, owned by someone else. Skipping.${C_RESET}\n"
+                continue
+            fi
+        fi
+
         # Check git config for this project to see if we should ignore this repo.
         IGNORE=$(git config -f "$GIT_CONF" --bool mgitstatus.ignore)
         if [ "$IGNORE" = "true" ]; then