A tool for fetching code
Maybe sometimes better than copy-paste.
Peru is a tool for including other people's code in your projects. It fetches from anywhere -- git, hg, svn, tarballs -- and puts files wherever you like. Peru helps you track exact versions of your dependencies, so that your history is always reproducible. And it fits inside your scripts and Makefiles, so your build stays simple and foolproof.
If you build with
make, you don't have to do anything special when you
switch branches or pull new commits. Build tools notice those changes
without any help. But if you depend on other people's code, the tools
aren't so automatic anymore. You need to remember when to
git submodule update or
go get -u or
pip install -r. If you forget a step you can
break your build, or worse, you might build something wrong without
Peru wants you to automate dependency management just like you automate the rest of your build. It doesn't interfere with your source control or install anything global, so you can just throw it in at the start of a script and forget about it. It'll run every time, and your dependencies will never be out of sync. Simple, and fast as heck.
Peru supports Linux, macOS, and Windows. It requires python (3.5 or later) and git, and optionally hg and svn if you want fetch from those types of repos.
Use pip to install it:
pip install peru
Note that depending on how Python is set up on your machine, you might
need to use
sudo with that, and Python 3's pip might be called
Also, if you have to use Python 3.3 or 3.4, those were supported up to
Using OS package managers
On Arch Linux, you can install
peru from the
Homebrew has a Peru formula for macOS
brew install peru will install it running on the latest Python
version that Homebrew supports.
imports: rack_example: rack/ # This is where we want peru to put the module. git module rack_example: url: git://github.com/chneukirchen/rack.git
What the heck just happened?
Peru cloned Rack for you, and imported a copy of it under the
It also created a magical directory called
.peru to hold that clone and some
other business. If you're using source control, now would be a good time to put
these directories in your ignore list (like
.gitignore). You usually don't
want to check them in.
peru clean will make the imported directory disappear. Running
peru sync again will make it come back, and it'll be a lot faster this time,
because peru caches everything.
For a more involved example, let's use peru to manage some dotfiles. We're big
fans of the Solarized colorscheme, and
we want to get it working in both
ls all we need peru to
do is fetch a Solarized dircolors file. (That'll get loaded somewhere like
.bashrc, not included in this example.) For
vim we're going to need the
Solarized vim plugin,
and we also want Pathogen, which makes
plugin installation much cleaner. Here's the
imports: # The dircolors file just goes at the root of our project. dircolors: ./ # We're going to merge Pathogen's autoload directory into our own. pathogen: .vim/autoload/ # The Solarized plugin gets its own directory, where Pathogen expects it. vim-solarized: .vim/bundle/solarized/ git module dircolors: url: https://github.com/seebi/dircolors-solarized # Only copy this file. Can be a list of files. Accepts * and ** globs. pick: dircolors.ansi-dark curl module pathogen: url: https://codeload.github.com/tpope/vim-pathogen/tar.gz/v2.3 # Untar the archive after fetching. unpack: tar # After the unpack, use this subdirectory as the root of the module. export: vim-pathogen-2.3/autoload/ git module vim-solarized: url: https://github.com/altercation/vim-colors-solarized # Fetch this exact commit, instead of master or main. rev: 7a7e5c8818d717084730133ed6b84a3ffc9d0447
The contents of the
dircolors module are copied to the root of our repo. The
pick field restricts this to just one file,
pathogen module uses the
curl type instead of
git, and its URL points
to a tarball. (This is for the sake of an example. In real life you'd probably
git here too.) The
unpack field means that we get the contents of the
tarball rather than the tarball file itself. Because the module specifies an
export directory, it's that directory rather than the whole module that gets
copied to the import path,
.vim/autoload. The result is that Pathogen's
autoload directory gets merged with our own, which is the standard way to
vim-solarized module gets copied into its own directory under
which is where Pathogen will look for it. Note that it has an explicit
field, which tells peru to fetch that exact revision, rather than the default
main in git). That's a Super Serious Best Practice™,
because it means your dependencies will always be consistent, even when you
look at commits from a long time ago.
You really want all of your dependencies to have hashes, but editing those by hand is painful. The next section is about making that easier.
If you run
peru reup, peru will talk to each of your upstream repos, get
their latest versions, and then edit your
peru.yaml file with any updates. If
you don't have
peru.yaml checked into some kind of source control, you should
probably do that first, because the reup will modify it in place. When we reup
the example above, the changes look something like this:
diff --git a/peru.yaml b/peru.yaml index 15c758d..7f0e26b 100644 --- a/peru.yaml +++ b/peru.yaml @@ -6,12 +6,14 @@ imports: git module dircolors: url: https://github.com/seebi/dircolors-solarized pick: dircolors.ansi-dark + rev: a5e130c642e45323a22226f331cb60fd37ce564f curl module pathogen: url: https://codeload.github.com/tpope/vim-pathogen/tar.gz/v2.3 unpack: tar export: vim-pathogen-2.3/autoload/ + sha1: 9c3fd6d9891bfe2cd3ed3ddc9ffe5f3fccb72b6a git module vim-solarized: url: https://github.com/altercation/vim-colors-solarized - rev: 7a7e5c8818d717084730133ed6b84a3ffc9d0447 + rev: 528a59f26d12278698bb946f8fb82a63711eec21
Peru made three changes:
dircolorsmodule, which didn't have a
revbefore, just got one. By default for
git, this is the current
main. To change that, you can set the
reupfield to the name of a different branch.
pathogenmodule got a
curlmodule is plain old HTTP, so it's stuck downloading whatever file is at the
url. But it will check this hash after the download is finished, and it will raise an error if there's a mismatch.
vim-solarizedmodule had a hash before, but it's been updated. Again, the new value comes from
At this point, you'll probably want to make a new commit of
record the version bumps. You can do this every so often to keep your plugins
up to date, and you'll always be able to reach old versions in your history.
- Pull in your imports.
syncyells at you instead of overwriting existing or modified files. Use
-fto tell it you're serious.
- Pull in your imports.
- Remove imported files. Same
- Remove imported files. Same
- Update module fields with new revision information. For
svn, this updates the
curl, this sets the
sha1field. You can optionally give specific module names as arguments.
- Update module fields with new revision information. For
- Make a copy of all the files in a module. Either specify a directory to put them in, or peru will create a temp dir for you. You can use this to see modules you don't normally import, or to play with different module/rule combinations (see "Rules" below).
- Replace the contents of a module with a local directory path, usually a
clone you've made of the same repo. This lets you test changes to imported
modules without needing to push your changes upstream or edit
- Replace the contents of a module with a local directory path, usually a clone you've made of the same repo. This lets you test changes to imported modules without needing to push your changes upstream or edit
git, hg, svn
For cloning repos. These types all provide the same fields:
url: required, any protocol supported by the underlying VCS
rev: optional, the specific revision/branch/tag to fetch
reup: optional, the branch/tag to get the latest rev from when running
git type also supports setting
submodules: false to skip
fetching git submodules. Otherwise they're included by default.
For downloading a file from a URL. This type is powered by Pythons's standard library, rather than an external program.
url: required, any kind supported by
filename: optional, overrides the default filename
sha1: optional, checks that the downloaded file matches the checksum
Peru includes a few other types mostly for testing purposes. See
rsync for an
example implemented in Bash.
Creating New Module Types
Module type plugins are as-dumb-as-possible scripts that only know how to sync, and optionally reup. Peru shells out to them and then handles most of the caching magic itself, though plugins can also do their own caching as appropriate. For example, the git and hg plugins keep track of repos they clone. Peru itself doesn't need to know how to do that. For all the details, see Architecture: Plugins.
Some fields (like
unpack) are specific to certain module
types. There are also fields you can use in any module, which modify the
tree of files after it's fetched. Some of these made an appearance in
the fancy example above:
copy: A map or multimap of source and destination paths to copy. Works like
cpon the command line, so if the destination is a directory, it'll preserve the source filename and copy into the destination directory.
move: A map or multimap of source and destination paths to move. Similar to
copyabove, but removes the source.
drop: A file or directory, or a list of files and directories, to remove from the module. Paths can contain
pick: A file or directory, or a list of files and directories, to include in the module. Everything else is dropped. Paths can contain
executable: A file or list of files to make executable, as if calling
chmod +x. Also accepts globs.
export: A subdirectory that peru should treat as the root of the module tree. Everything else is dropped, including parent directories.
Note that these fields always take effect in the order listed above, regardless
of the order they're given in
peru.yaml. For example, a
move is always
performed before a
pick. Also note that these fields can't be given twice.
For example, instead of using two separate
move fields (one of which would be
ignored), use a single
move field containing multiple moves. In practice,
things work this way because these fields are parsed as keys in a dictionary,
which don't preserve ordering and can't repeat.
Besides using those fields in your modules, you can also use them in "named
rules", which let you transform one module in multiple ways. For example, say
you want the
asyncio subdir from the Tulip project, but you also want the
license file somewhere else. Rather than defining the same module twice, you
can use one module and two named rules, like this:
imports: tulip|asyncio: python/asyncio/ tulip|license: licenses/ git module tulip: url: https://github.com/python/asyncio rule asyncio: export: asyncio/ rule license: pick: COPYING
As in this example, named rules are declared a lot like modules and then
used in the
imports list, with the syntax
operator there works kind of like a shell pipeline, so you can even do
twisted things like
module|rule1|rule2, with each rule applying to the
output tree of the previous.
If you import a module that has a peru file of its own, peru can include
that module's imports along with it, similar to how git submodules
git clone --recursive. To enable this, add
recursive: true in a module's definition.
It's also possible to directly import modules that are defined in the
peru.yaml file of another module. If your project defines a module
foo has a peru file in it that defines a module
foo.bar in your own imports. This works even if you never
foo, and it does not require setting
There are several flags and environment variables you can set, to control where peru puts things. Flags always take precedence.
--file=<file>: The path to your peru YAML file. By default peru looks for
peru.yamlin the current directory or one of its parents. This setting tells peru to use a specific file. If set,
--sync-dirmust also be set.
--sync-dir=<dir>: The path that all
importsare interpreted relative to. That is, if you import a module to
./, the contents of that module go directly in the sync dir. By default this is the directory containing your
peru.yamlfile. If set,
--filemust also be set.
--state-dir=<dir>: The directory where peru stashes all of its state metadata, and also the parent of the cache dir. By default this is
.peruinside the sync dir. You should not share this directory between two projects, or
peru syncwill get confused.
PERU_CACHE_DIR: The directory where peru keeps everything it's fetched. If you have many projects fetching the same dependencies, you can use a shared cache dir to speed things up.
--file-basename=<name>: Change the default peru file name (normally
peru.yaml). As usual, peru will search the current directory and its parents for a file of that name, and it will use that file's parent dir as the sync dir. Incompatible with
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