merge(3p/git): Merge git subtree at v2.29.2 r/1890

This also bumps the stable nixpkgs to 20.09 as of 2020-11-21, because
there is some breakage in the git build related to the netrc
credentials helper which someone has taken care of in nixpkgs.

The stable channel is not used for anything other than git, so this
should be fine.

Change-Id: I3575a19dab09e1e9556cf8231d717de9890484fb

1 files changed, 174 insertions, 0 deletions

diff --git a/third_party/git/git-gui/README.md b/third_party/git/git-gui/README.md
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+# Git GUI - A graphical user interface for Git
+
+Git GUI allows you to use the [Git source control management
+tools](https://git-scm.com/) via a GUI. This includes staging, committing,
+adding, pushing, etc. It can also be used as a blame viewer, a tree browser,
+and a citool (make exactly one commit before exiting and returning to shell).
+More details about Git GUI can be found in its manual page by either running
+`man git-gui`, or by visiting the [online manual
+page](https://git-scm.com/docs/git-gui).
+
+Git GUI was initially written by Shawn O. Pearce, and is distributed with the
+standard Git installation.
+
+# Building and installing
+
+You need to have the following dependencies installed before you begin:
+
+- Git
+- Tcl
+- Tk
+- wish
+- Gitk (needed for browsing history)
+- msgfmt
+
+Most of Git GUI is written in Tcl, so there is no compilation involved. Still,
+some things do need to be done (mostly some substitutions), so you do need to
+"build" it.
+
+You can build Git GUI using:
+
+```
+make
+```
+
+And then install it using:
+
+```
+make install
+```
+
+You probably need to have root/admin permissions to install.
+
+# Contributing
+
+The project is currently maintained by Pratyush Yadav over at
+https://github.com/prati0100/git-gui. Even though the project is hosted at
+GitHub, the development does not happen over GitHub Issues and Pull Requests.
+Instead, an email based workflow is used. The Git mailing list
+[git@vger.kernel.org](mailto:git@vger.kernel.org) is where the patches are
+discussed and reviewed.
+
+More information about the Git mailing list and instructions to subscribe can
+be found [here](https://git.wiki.kernel.org/index.php/GitCommunity).
+
+## Sending your changes
+
+Since the development happens over email, you need to send in your commits in
+text format. Commits can be converted to emails via the two tools provided by
+Git: `git-send-email` and `git-format-patch`.
+
+You can use `git-format-patch` to generate patches in mbox format from your
+commits that can then be sent via email. Let's say you are working on a branch
+called 'foo' that was created on top of 'master'. You can run:
+
+```
+git format-patch -o output_dir master..foo
+```
+
+to convert all the extra commits in 'foo' into a set of patches saved in the
+folder `output_dir`.
+
+If you are sending multiple patches, it is recommended to include a cover
+letter. A cover letter is an email explaining in brief what the series is
+supposed to do. A cover letter template can be generated by passing
+`--cover-letter` to `git-format-patch`.
+
+After you send your patches, you might get a review suggesting some changes.
+Make those changes, and re-send your patch(es) in reply to the first patch of
+your initial version. Also please mention the version of the patch. This can be
+done by passing `-v X` to `git-format-patch`, where 'X' is the version number
+of the patch(es).
+
+### Using git-send-email
+
+You can use `git-send-email` to send patches generated via `git-format-patch`.
+While you can directly send patches via `git-send-email`, it is recommended
+that you first use `git-format-patch` to generate the emails, audit them, and
+then send them via `git-send-email`.
+
+A pretty good guide to configuring and using `git-send-email` can be found
+[here](https://www.freedesktop.org/wiki/Software/PulseAudio/HowToUseGitSendEmail/)
+
+### Using your email client
+
+If your email client supports sending mbox format emails, you can use
+`git-format-patch` to get an mbox file for each commit, and then send them. If
+there is more than one patch in the series, then all patches after the first
+patch (or the cover letter) need to be sent as replies to the first.
+`git-send-email` does this by default.
+
+### Using GitGitGadget
+
+Since some people prefer a GitHub pull request based workflow, they can use
+[GitGitGadget](https://gitgitgadget.github.io/) to send in patches. The tool
+was originally written for sending patches to the Git project, but it now also
+supports sending patches for git-gui.
+
+Instructions for using GitGitGadget to send git-gui patches, courtesy of
+Johannes Schindelin:
+
+If you don't already have a fork of the [git/git](https://github.com/git/git)
+repo, you need to make one. Then clone your fork:
+
+```
+git clone https://github.com/<your-username>/git
+```
+
+Then add GitGitGadget as a remote:
+
+```
+git remote add gitgitgadget https://github.com/gitgitgadget/git
+```
+
+Then fetch the git-gui branch:
+
+```
+git fetch gitgitgadget git-gui/master
+```
+
+Then create a new branch based on git-gui/master:
+
+```
+git checkout -b <your-branch-name> git-gui/master
+```
+
+Make whatever commits you need to, push them to your fork, and then head over
+to https://github.com/gitgitgadget/git/pulls and open a Pull Request targeting
+git-gui/master.
+
+GitGitGadget will welcome you with a (hopefully) helpful message.
+
+## Signing off
+
+You need to sign off your commits before sending them to the list. You can do
+that by passing the `-s` option to `git-commit`. You can also use the "Sign
+Off" option in Git GUI.
+
+A sign-off is a simple 'Signed-off-by: A U Thor \<author@example.com\>' line at
+the end of the commit message, after your explanation of the commit.
+
+A sign-off means that you are legally allowed to send the code, and it serves
+as a certificate of origin. More information can be found at
+[developercertificate.org](https://developercertificate.org/).
+
+## Responding to review comments
+
+It is quite likely your patches will get review comments. Those comments are
+sent on the Git mailing list as replies to your patch, and you will usually be
+Cc'ed in those replies.
+
+You are expected to respond by either explaining your code further to convince
+the reviewer what you are doing is correct, or acknowledge the comments and
+re-send the patches with those comments addressed.
+
+Some tips for those not familiar with communication on a mailing list:
+
+- Use only plain text emails. No HTML at all.
+- Wrap lines at around 75 characters.
+- Do not send attachments. If you do need to send some files, consider using a
+  hosting service, and paste the link in your email.
+- Do not [top post](http://www.idallen.com/topposting.html).
+- Always "reply all". Keep all correspondents and the list in Cc. If you reply
+  directly to a reviewer, and not Cc the list, other people would not be able
+  to chime in.