mirror of
https://github.com/romkatv/powerlevel10k
synced 2024-12-22 14:02:57 +00:00
530 lines
25 KiB
Markdown
530 lines
25 KiB
Markdown
# gitstatus
|
|
|
|
**gitstatus** is a 10x faster alternative to `git status` and `git describe`. Its primary use
|
|
case is to enable fast git prompt in interactive shells.
|
|
|
|
Heavy lifting is done by **gitstatusd** -- a custom binary written in C++. It comes with Zsh and
|
|
Bash bindings for integration with shell.
|
|
|
|
## Table of Contents
|
|
|
|
1. [Using from Zsh](#using-from-zsh)
|
|
1. [Using from Bash](#using-from-bash)
|
|
2. [Using from other shells](#using-from-other-shells)
|
|
1. [How it works](#how-it-works)
|
|
1. [Benchmarks](#benchmarks)
|
|
1. [Why fast](#why-fast)
|
|
1. [Requirements](#requirements)
|
|
1. [Compiling](#compiling)
|
|
1. [License](#license)
|
|
|
|
## Using from Zsh
|
|
|
|
The easiest way to take advantage of gitstatus from Zsh is to use a theme that's already integrated
|
|
with it. For example, [Powerlevel10k](https://github.com/romkatv/powerlevel10k) is a flexible and
|
|
fast theme with first-class gitstatus integration.
|
|
|
|
![Powerlevel10k Zsh Theme](
|
|
https://raw.githubusercontent.com/romkatv/powerlevel10k-media/master/prompt-styles-high-contrast.png)
|
|
|
|
For those who wish to use gitstatus without a theme, there is
|
|
[gitstatus.prompt.zsh](gitstatus.prompt.zsh). Install it as follows:
|
|
|
|
```zsh
|
|
git clone --depth=1 https://github.com/romkatv/gitstatus.git ~/gitstatus
|
|
echo 'source ~/gitstatus/gitstatus.prompt.zsh' >>! ~/.zshrc
|
|
```
|
|
|
|
Users in mainland China can use the official mirror on gitee.com for faster download.<br>
|
|
中国大陆用户可以使用 gitee.com 上的官方镜像加速下载.
|
|
|
|
```zsh
|
|
git clone --depth=1 https://gitee.com/romkatv/gitstatus.git ~/gitstatus
|
|
echo 'source ~/gitstatus/gitstatus.prompt.zsh' >>! ~/.zshrc
|
|
```
|
|
|
|
Alternatively, on macOS you can install with Homebrew:
|
|
|
|
```zsh
|
|
brew install romkatv/gitstatus/gitstatus
|
|
echo 'source /usr/local/opt/gitstatus/gitstatus.prompt.zsh' >>! ~/.zshrc
|
|
```
|
|
|
|
(If you choose this option, replace `~/gitstatus` with `/usr/local/opt/gitstatus` in all code
|
|
snippets below.)
|
|
|
|
_Make sure to disable your current theme if you have one._
|
|
|
|
This will give you a basic yet functional prompt with git status in it. It's
|
|
[over 10x faster](#benchmarks) than any alternative that can give you comparable prompt. In order
|
|
to customize it, set `PROMPT` and/or `RPROMPT` at the end of `~/.zshrc` after sourcing
|
|
`gitstatus.prompt.zsh`. Insert `${GITSTATUS_PROMPT}` where you want git status to go. For example:
|
|
|
|
```zsh
|
|
source ~/gitstatus/gitstatus.prompt.zsh
|
|
|
|
PROMPT='%~%# ' # left prompt: directory followed by %/# (normal/root)
|
|
RPROMPT='$GITSTATUS_PROMPT' # right prompt: git status
|
|
```
|
|
|
|
The expansion of `${GITSTATUS_PROMPT}` can contain the following bits:
|
|
|
|
| segment | meaning |
|
|
|-------------|-------------------------------------------------------|
|
|
| `master` | current branch |
|
|
| `#v1` | HEAD is tagged with `v1`; not shown when on a branch |
|
|
| `@5fc6fca4` | current commit; not shown when on a branch or tag |
|
|
| `⇣1` | local branch is behind the remote by 1 commit |
|
|
| `⇡2` | local branch is ahead of the remote by 2 commits |
|
|
| `⇠3` | local branch is behind the push remote by 3 commits |
|
|
| `⇢4` | local branch is ahead of the push remote by 4 commits |
|
|
| `*5` | there are 5 stashes |
|
|
| `merge` | merge is in progress (could be some other action) |
|
|
| `~6` | there are 6 merge conflicts |
|
|
| `+7` | there are 7 staged changes |
|
|
| `!8` | there are 8 unstaged changes |
|
|
| `?9` | there are 9 untracked files |
|
|
|
|
`$GITSTATUS_PROMPT_LEN` tells you how long `$GITSTATUS_PROMPT` is when printed to the console.
|
|
[gitstatus.prompt.zsh](gitstatus.prompt.zsh) has an example of using it to truncate the current
|
|
directory.
|
|
|
|
If you'd like to change the format of git status, or want to have greater control over the
|
|
process of assembling `PROMPT`, you can copy and modify parts of
|
|
[gitstatus.prompt.zsh](gitstatus.prompt.zsh) instead of sourcing the script. Your `~/.zshrc`
|
|
might look something like this:
|
|
|
|
```zsh
|
|
source ~/gitstatus/gitstatus.plugin.zsh
|
|
|
|
function my_set_prompt() {
|
|
PROMPT='%~%# '
|
|
RPROMPT=''
|
|
|
|
if gitstatus_query MY && [[ $VCS_STATUS_RESULT == ok-sync ]]; then
|
|
RPROMPT=${${VCS_STATUS_LOCAL_BRANCH:-@${VCS_STATUS_COMMIT}}//\%/%%} # escape %
|
|
(( VCS_STATUS_NUM_STAGED )) && RPROMPT+='+'
|
|
(( VCS_STATUS_NUM_UNSTAGED )) && RPROMPT+='!'
|
|
(( VCS_STATUS_NUM_UNTRACKED )) && RPROMPT+='?'
|
|
fi
|
|
|
|
setopt no_prompt_{bang,subst} prompt_percent # enable/disable correct prompt expansions
|
|
}
|
|
|
|
gitstatus_stop 'MY' && gitstatus_start -s -1 -u -1 -c -1 -d -1 'MY'
|
|
autoload -Uz add-zsh-hook
|
|
add-zsh-hook precmd my_set_prompt
|
|
```
|
|
|
|
This snippet is sourcing `gitstatus.plugin.zsh` rather than `gitstatus.prompt.zsh`. The former
|
|
defines low-level bindings that communicate with gitstatusd over pipes. The latter is a simple
|
|
script that uses these bindings to assemble git prompt.
|
|
|
|
Unlike [Powerlevel10k](https://github.com/romkatv/powerlevel10k), code based on
|
|
[gitstatus.prompt.zsh](gitstatus.prompt.zsh) is communicating with gitstatusd synchronously. This
|
|
can make your prompt slow when working in a large git repository or on a slow machine. To avoid
|
|
this problem, call `gitstatus_query` asynchronously as documented in
|
|
[gitstatus.plugin.zsh](gitstatus.plugin.zsh). This can be quite challenging.
|
|
|
|
## Using from Bash
|
|
|
|
The easiest way to take advantage of gitstatus from Bash is via
|
|
[gitstatus.prompt.sh](gitstatus.prompt.sh). Install it as follows:
|
|
|
|
```bash
|
|
git clone --depth=1 https://github.com/romkatv/gitstatus.git ~/gitstatus
|
|
echo 'source ~/gitstatus/gitstatus.prompt.sh' >> ~/.bashrc
|
|
```
|
|
|
|
Users in mainland China can use the official mirror on gitee.com for faster download.<br>
|
|
中国大陆用户可以使用 gitee.com 上的官方镜像加速下载.
|
|
|
|
```bash
|
|
git clone --depth=1 https://gitee.com/romkatv/gitstatus.git ~/gitstatus
|
|
echo 'source ~/gitstatus/gitstatus.prompt.sh' >> ~/.bashrc
|
|
```
|
|
|
|
Alternatively, on macOS you can install with Homebrew:
|
|
|
|
```zsh
|
|
brew install romkatv/gitstatus/gitstatus
|
|
echo 'source /usr/local/opt/gitstatus/gitstatus.prompt.sh' >> ~/.bashrc
|
|
```
|
|
|
|
(If you choose this option, replace `~/gitstatus` with `/usr/local/opt/gitstatus` in all code
|
|
snippets below.)
|
|
|
|
This will give you a basic yet functional prompt with git status in it. It's
|
|
[over 10x faster](#benchmarks) than any alternative that can give you comparable prompt.
|
|
|
|
![Bash Prompt with GitStatus](
|
|
https://raw.githubusercontent.com/romkatv/gitstatus/1ac366952366d89980b3f3484f270b4fa5ae4293/bash-prompt.png)
|
|
|
|
In order to customize your prompt, set `PS1` at the end of `~/.bashrc` after sourcing
|
|
`gitstatus.prompt.sh`. Insert `${GITSTATUS_PROMPT}` where you want git status to go. For example:
|
|
|
|
```bash
|
|
source ~/gitstatus/gitstatus.prompt.sh
|
|
|
|
PS1='\w ${GITSTATUS_PROMPT}\n\$ ' # directory followed by git status and $/# (normal/root)
|
|
```
|
|
|
|
The expansion of `${GITSTATUS_PROMPT}` can contain the following bits:
|
|
|
|
| segment | meaning |
|
|
|-------------|-------------------------------------------------------|
|
|
| `master` | current branch |
|
|
| `#v1` | HEAD is tagged with `v1`; not shown when on a branch |
|
|
| `@5fc6fca4` | current commit; not shown when on a branch or tag |
|
|
| `⇣1` | local branch is behind the remote by 1 commit |
|
|
| `⇡2` | local branch is ahead of the remote by 2 commits |
|
|
| `⇠3` | local branch is behind the push remote by 3 commits |
|
|
| `⇢4` | local branch is ahead of the push remote by 4 commits |
|
|
| `*5` | there are 5 stashes |
|
|
| `merge` | merge is in progress (could be some other action) |
|
|
| `~6` | there are 6 merge conflicts |
|
|
| `+7` | there are 7 staged changes |
|
|
| `!8` | there are 8 unstaged changes |
|
|
| `?9` | there are 9 untracked files |
|
|
|
|
If you'd like to change the format of git status, or want to have greater control over the
|
|
process of assembling `PS1`, you can copy and modify parts of
|
|
[gitstatus.prompt.sh](gitstatus.prompt.sh) instead of sourcing the script. Your `~/.bashrc` might
|
|
look something like this:
|
|
|
|
```bash
|
|
source ~/gitstatus/gitstatus.plugin.sh
|
|
|
|
function my_set_prompt() {
|
|
PS1='\w'
|
|
|
|
if gitstatus_query && [[ "$VCS_STATUS_RESULT" == ok-sync ]]; then
|
|
if [[ -n "$VCS_STATUS_LOCAL_BRANCH" ]]; then
|
|
PS1+=" ${VCS_STATUS_LOCAL_BRANCH//\\/\\\\}" # escape backslash
|
|
else
|
|
PS1+=" @${VCS_STATUS_COMMIT//\\/\\\\}" # escape backslash
|
|
fi
|
|
(( VCS_STATUS_HAS_STAGED" )) && PS1+='+'
|
|
(( VCS_STATUS_HAS_UNSTAGED" )) && PS1+='!'
|
|
(( VCS_STATUS_HAS_UNTRACKED" )) && PS1+='?'
|
|
fi
|
|
|
|
PS1+='\n\$ '
|
|
|
|
shopt -u promptvars # disable expansion of '$(...)' and the like
|
|
}
|
|
|
|
gitstatus_stop && gitstatus_start
|
|
PROMPT_COMMAND=my_set_prompt
|
|
```
|
|
|
|
This snippet is sourcing `gitstatus.plugin.sh` rather than `gitstatus.prompt.sh`. The former
|
|
defines low-level bindings that communicate with gitstatusd over pipes. The latter is a simple
|
|
script that uses these bindings to assemble git prompt.
|
|
|
|
Note: Bash bindings, unlike Zsh bindings, don't support asynchronous calls.
|
|
|
|
## Using from other shells
|
|
|
|
If there are no gitstatusd bindings for your shell, you'll need to get your hands dirty.
|
|
Use the existing bindings for inspiration; run `gitstatusd --help` or read the same thing in
|
|
[options.cc](src/options.cc).
|
|
|
|
## How it works
|
|
|
|
gitstatusd reads requests from stdin and prints responses to stdout. Requests contain an ID and
|
|
a directory. Responses contain the same ID and machine-readable git status for the directory.
|
|
gitstatusd keeps some state in memory for the directories it has seen in order to serve future
|
|
requests faster.
|
|
|
|
[Zsh bindings](gitstatus.plugin.zsh) and [Bash bindings](gitstatus.plugin.sh) start gitstatusd in
|
|
the background and communicate with it via pipes. Themes such as
|
|
[Powerlevel10k](https://github.com/romkatv/powerlevel10k) use these bindings to put git status in
|
|
`PROMPT`.
|
|
|
|
Note that gitstatus cannot be used as a drop-in replacement for `git status` command as it doesn't
|
|
produce output in the same format. It does perform the same computation though.
|
|
|
|
## Benchmarks
|
|
|
|
The following benchmark results were obtained on Intel i9-7900X running Ubuntu 18.04 in
|
|
a clean [chromium](https://github.com/chromium/chromium) repository synced to `9394e49a`. The
|
|
repository was checked out to an ext4 filesystem on M.2 SSD.
|
|
|
|
Three functionally equivalent tools for computing git status were benchmarked:
|
|
|
|
* `gitstatusd`
|
|
* `git` with untracked cache enabled
|
|
* `lg2` -- a demo/example executable from [libgit2](https://github.com/romkatv/libgit2) that
|
|
implements a subset of `git` functionality on top of libgit2 API; for the purposes of this
|
|
benchmark the subset is sufficient to generate the same data as the other tools
|
|
|
|
Every tool was benchmark in cold and hot conditions. For `git` the first run in a repository was
|
|
considered cold, with the following runs considered hot. `lg2` was patched to compute results twice
|
|
in a single invocation without freeing the repository in between; the second run was considered hot.
|
|
The same patching was not done for `git` because `git` cannot be easily modified to refresh inmemory
|
|
index state between invocations; in fact, this limitation is one of the primary reasons developers
|
|
use libgit2. `gitstatusd` was benchmarked similarly to `lg2` with two result computations in the
|
|
same invocation.
|
|
|
|
Two commands were benchmarked: `status` and `describe`.
|
|
|
|
### Status
|
|
|
|
In this benchmark all tools were computing the equivalent of `git status`. Lower numbers are better.
|
|
|
|
| Tool | Cold | Hot |
|
|
|---------------|-----------:|------------:|
|
|
| **gitstatus** | **291 ms** | **30.9 ms** |
|
|
| git | 876 ms | 295 ms |
|
|
| lg2 | 1730 ms | 1310 ms |
|
|
|
|
gitstatusd is substantially faster than the alternatives, especially on hot runs. Note that hot runs
|
|
are of primary importance to the main use case of gitstatus in interactive shells.
|
|
|
|
The performance of `git status` fluctuated wildly in this benchmarks for reasons unknown to the
|
|
author. Moreover, performance is sticky -- once `git status` settles around a number, it stays
|
|
there for a long time. Numbers as diverse as 295, 352, 663 and 730 had been observed on hot runs on
|
|
the same repository. The number in the table is the lowest (fastest or best) that `git status` had
|
|
shown.
|
|
|
|
### Describe
|
|
|
|
In this benchmark all tools were computing the equivalent of `git describe --tags --exact-match`
|
|
to find tags that resolve to the same commit as `HEAD`. Lower numbers are better.
|
|
|
|
| Tool | Cold | Hot |
|
|
|---------------|------------:|--------------:|
|
|
| **gitstatus** | **4.04 ms** | **0.0345 ms** |
|
|
| git | 18.0 ms | 14.5 ms |
|
|
| lg2 | 185 ms | 45.2 ms |
|
|
|
|
gitstatusd is once again faster than the alternatives, more so on hot runs.
|
|
|
|
## Why fast
|
|
|
|
Since gitstatusd doesn't have to print all staged/unstaged/untracked files but only report
|
|
whether there are any, it can terminate repository scan early. It can also remember which files
|
|
were dirty on the previous run and check them first on the next run to avoid the scan entirely if
|
|
the files are still dirty. However, the benchmarks above were performed in a clean repository where
|
|
these shortcuts do not trigger. All benchmarked tools had to do the same work -- check the status
|
|
of every file in the index to see if it has changed, check every directory for newly created files,
|
|
etc. And yet, gitstatusd came ahead by a large margin. This section describes what it does that
|
|
makes it so fast.
|
|
|
|
Most of the following comparisons are done against libgit2 rather than git because of the author's
|
|
familiarity with the former but not the with latter. libgit2 has clean, well-documented APIs and an
|
|
elegant implementation, which makes it so much easier to work with and to analyze performance
|
|
bottlenecks.
|
|
|
|
### Summary for the impatient
|
|
|
|
Under the benchmark conditions described above, the equivalent of libgit2's
|
|
`git_diff_index_to_workdir` (the most expensive part of `status` command) is 46.3 times faster in
|
|
gitstatusd. The speedup comes from the following sources.
|
|
|
|
* gitstatusd uses more efficient data structures and algorithms and employs performance-conscious
|
|
coding style throughout the codebase. This reduces CPU time in userspace by 32x compared to libgit2.
|
|
* gitstatusd uses less expensive system calls and makes fewer of them. This reduces CPU time spent
|
|
in kernel by 1.9x.
|
|
* gitstatusd can utilize multiple cores to scan index and workdir in parallel with almost perfect
|
|
scaling. This reduces total run time by 12.4x while having virtually no effect on total CPU time.
|
|
|
|
### Problem statement
|
|
|
|
The most resource-intensive part of the `status` command is finding the difference between _index_
|
|
and _workdir_ (`git_diff_index_to_workdir` in libgit2). Index is a list of all files in the git
|
|
repository with their last modification times. This is an obvious simplification but it suffices for
|
|
this exposition. On disk, index is stored sorted by file path. Here's an example of git index:
|
|
|
|
| File | Last modification time |
|
|
|-------------|-----------------------:|
|
|
| Makefile | 2019-04-01T14:12:32Z |
|
|
| src/hello.c | 2019-04-01T14:12:00Z |
|
|
| src/hello.h | 2019-04-01T14:12:32Z |
|
|
|
|
This list needs to be compared to the list of files in the working directory. If any of the files
|
|
listed in the index are missing from the workdir or have different last modification time, they are
|
|
"unstaged" in gitstatusd parlance. If you run `git status`, they'll be shown as "changes not staged
|
|
for commit". Thus, any implementation of `status` command has to call `stat()` or one of its
|
|
variants on every file in the index.
|
|
|
|
In addition, all files in the working directory for which there is no entry in the index at all are
|
|
"untracked". `git status` will show them as "untracked files". Finding untracked files requires some
|
|
form of work directory traversal.
|
|
|
|
### Single-threaded scan
|
|
|
|
Let's see how `git_diff_index_to_workdir` from libgit2 accomplishes these tasks. Here's its CPU
|
|
profile from 200 hot runs over chromium repository.
|
|
|
|
![libgit2 CPU profile (hot)](
|
|
https://raw.githubusercontent.com/romkatv/gitstatus/1ac366952366d89980b3f3484f270b4fa5ae4293/cpu-profile-libgit2.png)
|
|
|
|
(The CPU profile was created with [gperftools](https://github.com/gperftools/gperftools) and
|
|
rendered with [pprof](https://github.com/google/pprof)).
|
|
|
|
We can see `__GI__lxstat` taking a lot of time. This is the `stat()` call for every file in the
|
|
index. We can also identify `__opendir`, `__readdir` and `__GI___close_nocancel` -- glibc wrappers
|
|
for reading the contents of a directory. This is for finding untracked files. Out of the total 232
|
|
seconds, 111 seconds -- or 47.7% -- was spent on these calls. The rest is computation -- comparing
|
|
strings, sorting arrays, etc.
|
|
|
|
Now let's take a look at the CPU profile of gitstatusd on the same task.
|
|
|
|
![gitstatusd CPU profile (hot)](
|
|
https://raw.githubusercontent.com/romkatv/gitstatus/1ac366952366d89980b3f3484f270b4fa5ae4293/cpu-profile-gitstatusd-hot.png)
|
|
|
|
The first impression is that this profile looks pruned. This isn't an artifact. The profile was
|
|
generated with the same tools and the same flags as the profile of libgit2.
|
|
|
|
Since both profiles were generated from the same workload, absolute numbers can be compared. We can
|
|
see that gitstatusd took 62 seconds in total compared to libgit2's 232 seconds. System calls at the
|
|
core of the algorithm are cleary visible. `__GI___fxstatat` is a flavor of `stat()`, and the other
|
|
three calls -- `__libc_openat64`, `__libc_close` and `__GI___fxstat` are responsible for opening
|
|
directories and finding untracked files. Notice that there is almost nothing else in the profile
|
|
apart from these calls. The rest of the code accounts for 3.77 seconds of CPU time -- 32 times less
|
|
than in libgit2.
|
|
|
|
So, one reason gitstatusd is fast is that it has efficient diffing code -- very little time is spent
|
|
outside of kernel. However, if we look closely, we can notice that system calls in gitstatusd are
|
|
_also_ faster than in libgit2. For example, libgit2 spent 72.07 seconds in `__GI__lxstat` while
|
|
gitstatusd spent only 48.82 seconds in `__GI___fxstatat`. There are two reasons for this difference.
|
|
First, libgit2 makes more `stat()` calls than is strictly required. It's not necessary to stat
|
|
directories because index only has files. There are 25k directories in chromium repository (and 300k
|
|
files) -- that's 25k `stat()` calls that could be avoided. The second reason is that libgit2 and
|
|
gitstatusd use different flavors of `stat()`. libgit2 uses `lstat()`, which takes a path to the file
|
|
as input. Its performance is linear in the number of subdirectories in the path because it needs to
|
|
perform a lookup for every one of them and to check permissions. gitstatusd uses `fstatat()`, which
|
|
takes a file descriptor to the parent directory and a name of the file. Just a single lookup, less
|
|
CPU time.
|
|
|
|
Similarly to `lstat()` vs `fstatat()`, it's faster to open files and directories with `openat()`
|
|
from the parent directory file descriptor than with regular `open()` that accepts full file path.
|
|
gitstatusd takes advantage of `openat()` to open directories as fast as possible. It opens about 90%
|
|
of the directories (this depends on the actual directory structure of the repository) from the
|
|
immediate parent -- the most efficient way -- and the remaining 10% it opens from the repository's
|
|
root directory. The reason it's done this way is to keep the maximum number of simultaneously open
|
|
file descriptors bounded. libgit2 can have O(repository depth) simultaneously open file descriptors,
|
|
which may be OK for a single-threaded application but can balloon to a large number when scans are
|
|
done by many threads simultaneously, like in gitstatusd.
|
|
|
|
There is no equivalent to `__opendir` or `__readdir` in the gitstatusd profile because it uses the
|
|
equivalent of [untracked cache](https://git-scm.com/docs/git-update-index#_untracked_cache) from
|
|
git. On the first scan of the workdir gitstatusd lists all files just like libgit2. But, unlike
|
|
libgit2, it remembers the last modification time of every directory along with the list of
|
|
untracked files under it. On the next scan, gitstatusd can skip listing files in directories whose
|
|
last modification time hasn't changed.
|
|
|
|
To summarize, here's what gitstatusd was doing when the CPU profile was captured:
|
|
|
|
1. `__libc_openat64`: Open every directory for which there are files in the index.
|
|
2. `__GI___fxstat`: Check last modification time of the directory. Since it's the same as on the
|
|
last scan, this directory has the same list of untracked files as before, which is empty (the
|
|
repository is clean).
|
|
3. `__GI___fxstatat`: Check last modification time for every file in the index that belongs to this
|
|
directory.
|
|
4. `__libc_close`: Close the file descriptor to the directory.
|
|
|
|
Here's how the very first scan of a repository looks like in gitstatusd:
|
|
|
|
![gitstatusd CPU profile (cold)](
|
|
https://raw.githubusercontent.com/romkatv/gitstatus/1ac366952366d89980b3f3484f270b4fa5ae4293/cpu-profile-gitstatusd-cold.png)
|
|
|
|
(Some glibc functions are mislabel on this profile. `explicit_bzero` and `__nss_passwd_lookup` are
|
|
in reality `strcmp` and `memcmp`.)
|
|
|
|
This is a superset of the previous -- hot -- profile, with an extra `syscall` and string sorting for
|
|
directory listing. gitstatusd uses `getdents64` Linux system call directly, bypassing the glibc
|
|
wrapper that libgit2 uses. This is 23% faster. The details of this optimization can be found in a
|
|
[separate document](docs/listdir.md).
|
|
|
|
### Multithreading
|
|
|
|
The diffing algorithm in gitstatusd was designed from the ground up with the intention of using it
|
|
concurrently from multiple threads. With a fast SSD, `status` is CPU bound, so taking advantage of
|
|
all available CPU cores is an obvious way to yield results faster.
|
|
|
|
gitstatusd exhibits almost perfect scaling from multithreading. Engaging all cores allows it to
|
|
produce results 12.4 times faster than in single-threaded execution. This is on Intel i9-7900X with
|
|
10 cores (20 with hyperthreading) with single-core frequency of 4.3GHz and all-core frequency of
|
|
4.0GHz.
|
|
|
|
Note: `git status` also uses all available cores in some parts of its algorithm while `lg2` does
|
|
everything in a single thread.
|
|
|
|
### Postprocessing
|
|
|
|
Once the difference between the index and the workdir is found, we have a list of _candidates_ --
|
|
files that may be unstaged or untracked. To make the final judgement, these files need to be checked
|
|
against `.gitignore` rules and a few other things.
|
|
|
|
gitstatusd uses [patched libgit2](https://github.com/romkatv/libgit2) for this step. This fork
|
|
adds several optimizations that make libgit2 faster. The patched libgit2 performs more than twice
|
|
as fast in the benchmark as the original even without changes in the user code (that is, in the
|
|
code that uses the libgit2 APIs). The fork also adds several API extensions, most notable of which
|
|
is the support for multi-threaded scans. If `lg2 status` is modified to take advantage of these
|
|
extensions, it outperforms the original libgit2 by a factor of 18. Lastly, the fork fixes a score of
|
|
bugs, most of which become apparent only when using libgit2 from multiple threads.
|
|
|
|
_WARNING: Changes to libgit2 are extensive but the testing they underwent isn't. It is
|
|
**not recommended** to use the patched libgit2 in production._
|
|
|
|
## Requirements
|
|
|
|
* To compile: binutils, cmake, gcc, g++, git and GNU make.
|
|
* To run: Linux, macOS, FreeBSD, Android, WSL, Cygwin or MSYS2.
|
|
|
|
## Compiling
|
|
|
|
There are prebuilt `gitstatusd` binaries in [releases](
|
|
https://github.com/romkatv/gitstatus/releases). When using the official shell bindings
|
|
provided by gitstatus, the right binary for your architecture gets downloaded automatically.
|
|
|
|
If prebuilt binaries don't work for you, you'll need to get your hands dirty.
|
|
|
|
### Compiling for personal use
|
|
|
|
```zsh
|
|
git clone --depth=1 https://github.com/romkatv/gitstatus.git
|
|
cd gitstatus
|
|
./build -w -s -d docker
|
|
```
|
|
|
|
Users in mainland China can use the official mirror on gitee.com for faster download.<br>
|
|
中国大陆用户可以使用 gitee.com 上的官方镜像加速下载.
|
|
|
|
```zsh
|
|
git clone --depth=1 https://gitee.com/romkatv/gitstatus.git
|
|
cd gitstatus
|
|
./build -w -s -d docker
|
|
```
|
|
|
|
- If it says that `-d docker` is not supported on your OS, remove this flag.
|
|
- If it says that `-s` is not supported on your OS, remove this flag.
|
|
- If it tell you to install docker but you cannot or don't want to, remove `-d docker`.
|
|
- If it says that some command is missing, install it.
|
|
|
|
If everything goes well, the newly built binary will appear in `./usrbin`. It'll be picked up
|
|
by shell bindings automatically.
|
|
|
|
When you update shell bindings, they may refuse to work with the binary you've built earlier. In
|
|
this case you'll need to rebuild.
|
|
|
|
If you are using gitstatus through [Powerlevel10k](https://github.com/romkatv/powerlevel10k), the
|
|
instructions are the same except that you don't need to clone gitstatus. Instead, change your
|
|
current directory to `/path/to/powerlevel10k/gitstatus` (`/path/to/powerlevel10k` is the directory
|
|
where you've installed Powerlevel10k) and run `./build -w -s -d docker` from there as described
|
|
above.
|
|
|
|
### Compiling for distribution
|
|
|
|
It's currently neither easy nor recommended to package and distribute gitstatus. There are no
|
|
instructions you can follow that would allow you to easily update your package when new versions of
|
|
gitstatus are released. This may change in the future but not soon.
|
|
|
|
## License
|
|
|
|
GNU General Public License v3.0. See [LICENSE](LICENSE). Contributions are covered by the same
|
|
license.
|