Add the script and reword README

README.md

@@ -1,3 +1,3 @@
 # git-force
 
-small utility to explain a force push before pushing, to help prevent accidents with git fetch and --force-with-lease
+A small utility to display what commits will be dropped and which will be added, and attempts to prevent overwrites with `--force-with-lease` from programs that repeadetly `git fetch`, and double checks remote and local to error out if any changed after confirming.

git-force

@@ -0,0 +1,131 @@
+#!/bin/bash
+if [[ "$1" == "--help" || "$1" == "-h" ]]
+then
+    echo "Usage:"
+    echo "    git force"
+    echo "    git force <remote>"
+    echo "    git force <remote> <branch>"
+    exit 0
+fi
+REMOTE=""
+BRANCH=""
+PRETTY="--pretty=format:%h, %an <%ae>, %ar: %s"
+if [[ "$#" == "0" ]]
+then
+    BRANCH="$(git branch --show-current)"
+    if [[ "$BRANCH" == "" ]]
+    then
+        echo "error: currently in detached HEAD state" >&2
+        exit 1
+    fi
+fi
+if [[ "$#" -gt "0" ]]
+then
+    REMOTE="$1"
+    git config "remote.$REMOTE.url" > /dev/null 2>&1
+    if [[ "$?" != "0" ]]
+    then
+        echo "error: specified remote is invalid" >&2
+        exit 2
+    fi
+fi
+if [[ "$#" -gt "1" ]]
+then
+    BRANCH="$2"
+    git rev-parse --verify "$BRANCH" > /dev/null 2>&1
+    if [[ "$?" != "0" ]]
+    then
+        echo "error: specified branch is invalid" >&2
+        exit 3
+    fi
+fi
+if [[ "$REMOTE" == "" ]]
+then
+    REMOTE=$(git config "branch.$BRANCH.remote")
+    if [[ "$?" != "0" ]]
+    then
+        echo "error: current branch does not have a remote and no remote was specified" >&2
+        echo "see: git force --help"
+        exit 4
+    fi
+fi
+if [[ "$REMOTE" == "" || "$BRANCH" == "" ]]
+then
+    echo "assertion failed: remote or branch is blank" >&2
+    exit 5
+fi
+REMOTE_BRANCH="$REMOTE/$BRANCH"
+REMOTE_HASH="$(git rev-parse "$REMOTE_BRANCH")" # later used to throw errors if something changes remote or local
+if [[ "$?" != "0" || "$REMOTE_HASH" == "" ]]
+then
+    echo "internal error: failed to fetch remote hash" >&2
+    exit 5
+fi
+LOCAL_HASH="$(git rev-parse "$BRANCH")"         # as that may cause the user unintentionally pushing/overwriting unwanted things
+if [[ "$?" != "0" || "$LOCAL_HASH" == "" ]]
+then
+    echo "internal error: failed to fetch local hash" >&2
+    exit 5
+fi
+
+if [[ "$REMOTE_HASH" == "$LOCAL_HASH" ]]
+then
+    echo "error: the branches are already the same" >&2
+    exit 8
+fi
+
+if [[ "$REMOTE_HASH" == "$FORK_POINT" ]]
+then
+    echo "error: the branches have not diverged" >&2
+    exit 9
+fi
+
+FORK_POINT="$(git merge-base "$BRANCH" "$REMOTE_BRANCH")"
+if [[ "$?" != "0" ]]
+then
+echo "The branches do not have a common ancestor, the latest commits for each are listed below:"
+echo ""
+echo "remote:"
+git show -s "$PRETTY" "$REMOTE_HASH"
+echo ""
+echo "remote:"
+git show -s "$PRETTY" "$REMOTE_HASH"
+else
+echo "The following commits will be OVERWRITTEN:"
+git log "$PRETTY" "$FORK_POINT..$REMOTE_HASH"
+echo ""
+echo "The following commits will overwrite the above commits:"
+git log "$PRETTY" "$FORK_POINT..$LOCAL_HASH"
+fi
+echo ""
+read -p "Continue? [y/N] " SHOULD_CONTINUE
+if [[ "$SHOULD_CONTINUE" != "y" ]]
+then
+echo "Abort." >&2
+exit 6
+fi
+REMOTE_HASH_2="$(git rev-parse "$REMOTE_BRANCH")"
+LOCAL_HASH_2="$(git rev-parse "$BRANCH")"
+if [[ "$REMOTE_HASH_2" != "$REMOTE_HASH" ]]
+then
+echo "@@@@@@@@@@@@@@@@@@@@@@@@@" >&2
+echo "@  REMOTE HAS UPDATED!  @" >&2
+echo "@@@@@@@@@@@@@@@@@@@@@@@@@" >&2
+echo "" >&2
+echo "The remote updated from $REMOTE_HASH"
+echo "to $REMOTE_HASH_2 while you were confirming."
+echo "Please re-run this command and check again."
+exit 7
+fi
+if [[ "$LOCAL_HASH_2" != "$LOCAL_HASH" ]]
+then
+echo "@@@@@@@@@@@@@@@@@@@@@@@@" >&2
+echo "@  LOCAL HAS UPDATED!  @" >&2
+echo "@@@@@@@@@@@@@@@@@@@@@@@@" >&2
+echo "" >&2
+echo "The local updated from $LOCAL_HASH"
+echo "to $LOCAL_HASH_2 while you were confirming."
+echo "Please re-run this command and check again."
+exit 7
+fi
+git push --force-with-lease "$REMOTE" "$BRANCH"