Add git workflow guidelines (#2688)

Resolves #1884

Author: patiencedaur

doc/contributing/docs.rst

@@ -20,3 +20,4 @@ The guidelines are a work in progress, and we welcome all contributions.
     docs/build
     docs/sphinx-warnings
     docs/infra
+    docs/git

doc/contributing/docs/git.rst

@@ -0,0 +1,97 @@
+Git workflow
+============
+
+Branching
+---------
+
+Use one branch for a single task, unless you're fixing typos or markup on several pages.
+Long commit histories are hard to manage and sometimes end up stale.
+
+Start a new branch from the last commit on ``latest``.
+Make sure to update your local version of ``latest`` with ``git pull``.
+Otherwise, you may have to rebase later.
+
+Name your branch so it's clear what you're doing. Examples:
+
+*   ``short-issue-description``
+*   ``gh-1234-short-issue-description``
+*   ``your-github-handle/short-issue-description``
+
+Linking issues and PRs
+----------------------
+
+When a PR is linked to an issue:
+
+*   You can go from the issue straight to the PR by clicking the link in the right column.
+*   The issue will be automatically closed when you close the PR.
+
+Specify the issue(s) you want to close in the description of your PR. GitHub will connect them if you use specific
+`keywords <https://docs.github.com/en/issues/tracking-your-work-with-issues/linking-a-pull-request-to-an-issue#linking-a-pull-request-to-an-issue-using-a-keyword>`__.
+Here are some of them:
+
+*   Closes #1234
+*   Resolves #1234
+*   Fixes #1234
+
+If your PR closes more than one issue, mention each of them:
+
+..  code-block::
+
+    Resolves #1300, resolves #1234, resolves tarantool/doc#100
+
+Commit messages
+---------------
+
+*   Most of the time, one-line commit messages are sufficient for documentation changes.
+
+    -   When you squash commits at merge, the resulting commit message is a sum of all commit messages in the PR.
+        It is advised to include the "resolves" string in the first commit.
+        Otherwise, there's a risk that this line won't be included in the merge commit.
+
+*   Convey the nature of the change and possibly the reason why it was made.
+
+    -   Don't specify the files you've changed or the issue you're working on.
+        The file names can be looked up in the "Files" section of the PR, and the PR description has the issue number(s).
+
+*   Try keeping the commit title 50 characters or shorter.
+*   Use the imperative mood.
+*   Start with a capital letter, don't add ending punctuation.
+*   (Optional) Use the telegraphic style, or "headlinese", dropping the articles.
+
+Good examples
+~~~~~~~~~~~~~
+
+*   ``git commit -m "Expand section on msgpack"``
+*   ``git commit -m "Add details on IPROTO_BALLOT"``
+*   ``git commit -m "Create new structure"``
+*   ``git commit -m "Improve grammar"``
+
+Bad examples
+~~~~~~~~~~~~
+
+*   ``git commit -m "Fix gh-2007, second commit"``
+*   ``git commit -m “Changed the file box_protocol.rst”``
+*   ``git commit -m "added more list items"``
+
+Selecting a reviewer
+--------------------
+
+Ideally, a PR should have two reviewers: a subject matter expert (SME) and a documentarian.
+The SME checks the facts, and the documentarian checks the language and style.
+
+If you're not sure who the SME for an issue is, try the following:
+
+*   Check the issue description. The SME is often mentioned there explicitly.
+*   Note who created the issue and who was involved in the discussion.
+
+Merging
+-------
+
+Merge when your document is ready and good enough.
+For external contributors, merging is blocked until a reviewer's approval.
+
+*   Always squash commits.
+*   Make sure the commit message mentions all relevant issues with "resolves" or "fixes".
+*   Make sure you've
+    `attributed <https://docs.github.com/en/pull-requests/committing-changes-to-your-project/creating-and-editing-commits/creating-a-commit-with-multiple-authors>`__
+    all participants with ``Co-authored-by``.