Use git-subrepo for the tools/ directory

tools/.gitrepo

@@ -0,0 +1,12 @@
+; DO NOT EDIT (unless you know what you are doing)
+;
+; This subdirectory is a git "subrepo", and this file is maintained by the
+; git-subrepo command. See https://github.com/ingydotnet/git-subrepo#readme
+;
+[subrepo]
+	remote = tools-origin
+	branch = mongo-c-tools
+	commit = 7f8ff8e0a2f7f2639745c5b48ac1f9e10c0518fd
+	method = merge
+	cmdver = 0.4.6
+	parent = 291608fd93e57aed366c2483feb568f3f81c27a7

tools/README.md

@@ -0,0 +1,90 @@
+# `mongo-c-tools`
+
+This directory contains shared scripts and tools for native C and C++
+development.
+
+
+## As a Subrepo
+
+If this directory contains a `.gitrepo` file, then this directory is being
+tracked as a *subrepo* of some parent repository. If this file does not exist
+but a `.git/` directory *does* exist, then you are looking at the tools
+repository itself.
+
+[`git subrepo`](https://github.com/ingydotnet/git-subrepo) is a set of scripts
+and conventions for pushing/pulling/syncing changes in a subdirectory between
+different repositories with full history tracking. *Using* the contents of this
+directory does not require the `git subrepo` tool, but pushing and pulling
+changes in this subrepo directory will require `git subrepo` (or knowing
+the appropriate commands to execute for the same effect).
+
+If you are simply using these scripts, you do not have to deal with the subrepo
+commands. If you wish to modify/sync these scripts, read on below.
+
+
+### Preparing
+
+`git-subrepo` tracks a subrepo directory using a remote+branch pair as the
+"source of truth" for the subrepo contents. The remote+branch pair is fixed in
+the `.gitrepo` file. In this subrepo directory, the `remote` is not set to a
+URL, but to a name `tools-origin`. In order to push/pull, you will need to
+ensure that you have a `tools-origin` set to the proper URL. Unless you "know
+what you are doing", you will want to use the upstream `mongo-c-driver`
+repository as the remote:
+
+```sh
+$ git remote add tools-origin "[email protected]:mongodb/mongo-c-driver.git"
+```
+
+The content of this subrepo is contained by the disjoint branch `mongo-c-tools`,
+which contains only the history of this directory as the root.
+
+**NOTE** that doing a `git subrepo push` will send changes into the remote
+branch immediately without a PR! See below about how to push changes.
+
+
+### Pulling Changes
+
+If the remote copy of the subrepo has been updated (e.g. as part of another
+project's changes), then the local copy of this subrepo can be updated by using
+`git subrepo pull`:
+
+```sh
+$ git subrepo pull $this_subdir
+```
+
+**Note:**
+
+- Doing a `subrepo pull` requires that there be *no* unstaged changes in the
+  parent repository.
+- Pulling a subrepo will create a new commit on the current branch. This commit
+  contains the changes that were pulled from the remote, as well as an update to
+  the `.gitrepo` file.
+- If merge conflicts occur, you will find yourself in a copy of the disjoint
+  branch in order to perform a conflict resolution. Follow the instructions
+  from `git-subrepo` to handle the merge.
+
+
+### Modifying these Files
+
+Before modifying the contents of this directory, be sure that you have the
+latest changes from the remote branch according to the
+[*pulling changes*](#pulling-changes) section. This will avoid annoying merge
+conflicts.
+
+To modify the contents of this directory, simply update and commit them as one
+would do normally. If you want your changes to undergo review:
+
+1. Create a PR and go through code review as normal. Don't worry about the
+   subrepo at this step.
+2. Merge the PR as normal.
+3. Begin a new temporary branch `$tmp` for the subrepo update that points to the
+   merge commit that resulted from the PR merge.
+4. With the `$tmp` branch active, run `git subrepo push`. This will create a new
+   commit on `$tmp` and send the local changes into the remote.
+5. Run `git subrepo status` and verify that the `Pull Parent` of the subrepo
+   refers to the merge commit from the orginal PR.
+6. Merge the `$tmp` back into the base branch, either through a PR or by just
+   pushing it directly without a PR (the `git subrepo push` will only generate a
+   few lines of change in the `.gitrepo` file and won't be interesting to
+   review).