Re: Regression `git checkout $rev -b branch` while in a `--no-checkout` clone does not check out files

[Duy Nguyen <pclouds@gmail.com>]

On Wed, Jan 2, 2019 at 11:18 PM Anthony Sottile <asottile@umich.edu> wrote:
> heated a small room but here's the results of the bisect!
>
> fa655d8411cc2d7ffcf898e53a1493c737d7de68 is the first bad commit
> commit fa655d8411cc2d7ffcf898e53a1493c737d7de68
> Author: Ben Peart <Ben.Peart@microsoft.com>
> Date:   Thu Aug 16 18:27:11 2018 +0000
>
>     checkout: optimize "git checkout -b <new_branch>"

I did test this commit before and could not reproduce. But one thing I
did not notice is I set sparsecheckout on by default. which always
forces this optimization off Turning off sparse checkout, I could
indeed reproduce.

I plan to revert this commit anyway when the new command "git
switch-branch" comes. The optimization will be unconditionally in the
new command without this hack and users are encouraged to use that one
instead of "git checkout".

Meanwhile, let's see if Ben wants to fix this or revert it.

>
>     Skip merging the commit, updating the index and working directory if and
>     only if we are creating a new branch via "git checkout -b <new_branch>."
>     Any other checkout options will still go through the former code path.
>
>     If sparse_checkout is on, require the user to manually opt in to this
>     optimzed behavior by setting the config setting checkout.optimizeNewBranch
>     to true as we will no longer update the skip-worktree bit in the index, nor
>     add/remove files in the working directory to reflect the current sparse
>     checkout settings.
>
>     For comparison, running "git checkout -b <new_branch>" on a large
> repo takes:
>
>     14.6 seconds - without this patch
>     0.3 seconds - with this patch
>
>     Signed-off-by: Ben Peart <Ben.Peart@microsoft.com>
>     Signed-off-by: Junio C Hamano <gitster@pobox.com>
>
> :040000 040000 817bfb8ef961545a554005d42967b5ab7cfdb041
> e57e576d0d4fb7f25c12a5dcc7651ef6698e961b M    Documentation
> :040000 040000 c089f91f4532caa2a17e4f10a1a7ed3aa5d2023c
> 7cf16a0aa288f898a880ffefe82ee7506b83bef4 M    builtin
> :040000 040000 adfdb05964a692e03ee07d2e43841f6304d996bd
> 8681416093802b9051599ebea8f63f5a45968e6f M    t
> bisect run success
>
>
> Here's the script and invocations:
>
> ```
> #!/usr/bin/env bash
> set -euxo pipefail
>
> rm -rf "$PWD/prefix"
> make prefix="$PWD/prefix" -j8 install
> export PATH="$PWD/prefix/bin:$PATH"
>
> rm -rf src dest
>
> git --version
>
> git init src
> echo hi > src/a
> git -C src add .
> git -C src commit -m "initial commit"
> rev="$(git -C src rev-parse HEAD)"
>
> git clone --no-checkout src dest
> git -C dest checkout "$rev" -b branch
> test -f dest/a
>
> : 'SUCCESS!'
> ```
>
> ```
> git bisect begin
> git bisect bad HEAD
> git bisect good v2.17.1
> git bisect run ./bisect.sh
> ```
>
> Anthony



-- 
Duy