add git hash changes announcement (#977)

GIT-CHANGES-17-01-25.md

@@ -0,0 +1,37 @@
+Synchronizing your git history after large file removal on January 17, 2025
+---------------------------------------------------------------------------
+
+As a result from our migration into a monorepo which kept the git history from the legacy Open Catalyst repository,
+the `FAIRChem` repository was 10MB of files combined with ~350MB of git history for files that no longer exist, but
+were still present in the git history.
+
+We removed those files in order to reduce the repository size, but that resulted in changed commit hashes. If you are
+currently developing or planning to develop please do the following:
+
+**Do not force push anything or your PR will be rejected**
+
+1. Backup your current repo if you have local changes
+   ```bash
+       rsync -av current_repo backup_of_current_repo
+   ```
+2. Migrating a branch (without local changes)
+   If you do not have local changes in the branch you wish to keep, ontop of those already on the GitHub (remote)
+   > :warning: This will erase all local changes
+   ```bash
+      git reset --hard origin/branch_name
+   ```
+3. Migrating a branch (with local changes)
+   We need to first unstage any commits that are not present on the remote. To do this use https://github.com/FAIR-Chem/fairchem/tree/main
+   to find what the last commit was to the remote branch (the hash wont match, match the commit message). Find the last
+   matching commit in your local history, use git log to find this. Once you have the hash from git log, unstage these commits using,
+   ```bash
+     git reset --soft last_commit_on_remote
+   ```
+   Then stash the changes, hard reset to the remote, and pop the changes from stash
+   ```bash
+      git stash
+      git reset --hard origin/branch_name
+      git stash pop
+   ```
+
+If you encounter any issues please open an issue.

README.md

@@ -16,6 +16,8 @@
 
 `fairchem` is the [FAIR](https://ai.meta.com/research/) Chemistry's centralized repository of all its data, models, demos, and application efforts for materials science and quantum chemistry.
 
+> :warning: **If you cloned the repo before January 17, 2025 and are actively developing, please read [this announcement](GIT-CHANGES-17-01-25.md).**
+
 ### Documentation
 If you are looking for `Open-Catalyst-Project/ocp`, it can now be found at [`fairchem.core`](src/fairchem/core). Visit its corresponding documentation [here](https://fair-chem.github.io/).
 
@@ -45,9 +47,9 @@ from ase.optimize import LBFGS
 from fairchem.core import OCPCalculator
 
 # Set up your system as an ASE atoms object
-slab = fcc100('Cu', (3, 3, 3), vacuum=8)
+slab = fcc100("Cu", (3, 3, 3), vacuum=8)
 adsorbate = molecule("CO")
-add_adsorbate(slab, adsorbate, 2.0, 'bridge')
+add_adsorbate(slab, adsorbate, 2.0, "bridge")
 
 calc = OCPCalculator(
     model_name="EquiformerV2-31M-S2EF-OC20-All+MD",