Add git-precheck script

This is an alternative entrypoint primarily intended for use in other
scripts.  The purpose of git-precheck is to easily determine the state
of a git repository before going on to perform additional, possibly
disruptive work.

git-precheck tries to cover as many bases as possible - odd cases like
'merge in progress', 'cherry-pick in progress', etc.  By default, we
only exit success (0) if we are in a repo that is completely clean (no
file modifications or untracked files present) and has no ongoing
operation.

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

1 files changed, 94 insertions, 0 deletions

diff --git a/git-precheck b/git-precheck
new file mode 100755
index 0000000..9984bbb
--- /dev/null
+++ b/git-precheck
@@ -0,0 +1,94 @@
+#!/bin/sh
+
+usage() {
+    echo "git-precheck [--quiet] [--ignore-dirty] [--ignore-untracked]"
+    echo ""
+    echo "If the current working directory is inside a git repository, examine"
+    echo "the repo for any abnormal state and return an exit code indicating"
+    echo "the status.  If unclean, print a line of text describing the"
+    echo "condition."
+    echo ""
+    echo "  --quiet"
+    echo "      Don't actually print anything."
+    echo ""
+    echo "  --ignore-dirty"
+    echo "      Don't consider the presence of uncommitted changes to tracked"
+    echo "      files as an abnormal state."
+    echo ""
+    echo "  --ignore-untracked"
+    echo "      Don't consider the presence of untracked files as an abnormal"
+    echo "      state."
+    echo ""
+    echo "  Exit codes:"
+    echo "      0   If inside a repository and all checks return normal"
+    echo "      1   If untracked files detected"
+    echo "      2   If dirty/modified files detected"
+    echo "      3   If any ongoing git operation is in progress"
+    echo "      4   If not inside a git repository"
+    echo ""
+    echo "      Exit any other value on error or if 'precheck' operation is"
+    echo "      not completed, such as when viewing this help text."
+    exit 128
+}
+
+quiet=""
+ignore_dirty=""
+ignore_untracked=""
+
+while true; do
+    case "$1" in
+        --quiet) quiet="true" ;;
+        --ignore-dirty) ignore_dirty="true" ;;
+        --ignore-untracked) ignore_untracked="true" ;;
+        --help) usage ;;
+        -h) usage ;;
+        *) break
+    esac
+    shift
+done
+
+if [ $# -ne 0 ]; then
+    printf 'precheck: Unrecognized option given: %s\n' "$1"
+    exit 128
+fi
+
+check() {
+    if git rev-parse --verify "$1" >/dev/null 2>&1; then
+        [ -z "$quiet" ] && printf '\e[0;31m%s in progress\e[0m\n' "$2"
+        exit 3
+    fi
+}
+
+if ! [ "$(git rev-parse --is-inside-work-tree 2>/dev/null)" = "true" ]; then
+    [ -z "$quiet" ] && printf '\e[0;31mNot inside a git work tree\e[0m\n'
+    exit 4
+fi
+
+check MERGE_HEAD Merge
+check REBASE_HEAD Rebase
+check REVERT_HEAD Revert
+check CHERRY_PICK_HEAD Cherry-pick
+check BISECT_EXPECTED_REV Bisect
+
+if [ -e "$(git rev-parse --git-path rebase-apply 2>/dev/null)" ]; then
+    [ -z "$quiet" ] && printf '\e[0;31mrebase-apply (am) found\e[0m\n'
+    exit 3
+fi
+
+if [ -z "$ignore_dirty" ]; then
+    if git status --porcelain 2>/dev/null \
+            | grep --quiet --invert-match '^??'; then
+        [ -z "$quiet" ] && printf '\e[0;31mModified files detected\e[0m\n'
+        exit 2
+    fi
+fi
+
+if [ -z "$ignore_untracked" ]; then
+    if git status --porcelain 2>/dev/null \
+            | grep --quiet '^??'; then
+        [ -z "$quiet" ] && printf '\e[0;31mUntracked files detected\e[0m\n'
+        exit 1
+    fi
+fi
+
+exit 0