# NAME

`bpkg-repository-types` – repository types, structure, and URLs

# DESCRIPTION

This help topic describes the repository types recognized by `bpkg`, their structure, and the format of their URLs. Currently three types of repositories are supported: archive-based `pkg`, directory-based `dir`, and version control-based `git`.

The repository location may specify the repository type as part of the URL scheme component in the `type+protocol` form. For example:

    git+https://example.com/foo
    dir+file:///tmp/repo

Note that the explicit specification is only needed when the correct type cannot be guessed from the URL. See `bpkg-rep-add(1)` for details.

# PKG REPOSITORIES

A `pkg` repository is archive-based. That is, it contains a collection of various packages/versions as archive files. For more information on the structure of `pkg` repositories refer to The `build2` Package Manager Manual. The `pkg` repository location can be a local directory path or an `http(s)://` URL.

# DIR REPOSITORIES

A `dir` repository is directory-based. That is, it contains a collection of various packages as directories but only a single version per package can be present in such a repository. The `dir` repository location can be a local directory path or a `file://` URL.

A `dir` repository is expected to contain either the `manifest` or `packages.manifest` file in the root directory of the repository. If it only contains `manifest`, then it is assumed to be a simple, single-package repository with the `manifest` file being its package manifest. Otherwise, the `packages.manifest` file should list the locations of available packages as described in Package List Manifest for `dir` Repositories.

A `dir` repository may also contain the `repositories.manifest` file in the root directory of the repository. This file can be used to describe the repository itself as well as specify its prerequisite and complement repositories. See Repository List Manifest for details on the format and semantics of this file.

# GIT REPOSITORIES

A `git` repository is version control-based. That is, it normally contains multiple versions of the same package (but can also contain several, usually related, packages in the same repository).

A `git` repository has the same structure and manifest files as the `dir` repository. See Package List Manifest for `dir` Repositories and Repository List Manifest for details on their format and semantics.

Theoretically, a `git` repository may contain as many package versions as there are commits. Practically, however, we are normally only interested in a small subset of them while fetching and processing the necessary information for all of them could be prohibitively expensive. As a result, by default, only advertised tags in the `refs/tags/v*` form where the part after `v` is also a valid standard version are considered to be sources of useful package versions. These commits normally correspond to released versions and are called the default set. Note that only the latest revision of each such version is considered.

Instead of the default set, it is possible to provide a custom set of available versions by specifying one or more commit ids and/or references and/or reference patterns in the repository URL fragment (see `git-ls-remote(1)` for details on advertised references). For example:

    https://example.com/foo.git#v1.2.3
    https://example.com/foo.git#master
    https://example.com/foo.git#af234f56
    https://example.com/foo.git#tags/releases/*
    https://example.com/foo.git#HEAD,tags/v1.*.*,heads/feature-*

Furthermore, it is possible to expand (or narrow down) the default set using the special `##` fragment notation. For example:

    https://example.com/foo.git##HEAD     - default set plus HEAD
    https://example.com/foo.git##heads/*  - default set plus branches
    https://example.com/foo.git##-v1.*    - default set minus v1.*

A `git` repository URL fragment is a comma-separated list of reference filters in the following form:

`[refname][@commit]`

Either `refname`, `commit`, or both must be specified. If both are specified then `refname` is only used to minimize the amount of data fetched and `commit` is expected to belong to its history. For example:

    .../foo.git#master@48fba3625d65941bb85a39061bcf795d4949c778

The `refname` part can be an abbreviated commit id or an advertised reference or reference pattern under `refs/`. While `commit` must be the complete, 40-characters SHA1 that need not be advertised. For convenience, a 40-characters filter that consists of only hexadecimal digits is assumed to be `commit` even if not prefixed with `@`. In an unlikely event this produces an incorrect result, the `@`-form with omitted `commit` can be used. For example:

    .../foo.git#48fba3625d65941bb85a39061bcf795d4949c778   (commit id)
    .../foo.git#deadbeefdeadbeefdeadbeefdeadbeefdeadbeef@  (reference)

The `refname` part can use the `*` and `?` wildcard pattern characters with the standard semantics as well as the `**` character sequence which matches in subdirectories, recursively. For example:

    .../foo.git#tags/v*    - tags/v1.2.3 but not tags/old/v0.1.0
    .../foo.git#tags/v**   - tags/v1.2.3 and tags/old/v0.1.0

A relative `refname` is searched for in `refs/`, `refs/tags/`, and `refs/heads/` as well as among symbolic references like `HEAD`. To anchor it to `refs/` make it absolute, for example:

    .../foo.git#tags/v*   - refs/tags/v1.2.3 but also refs/heads/tags/voo
    .../foo.git#/tags/v*  - refs/tags/v1.2.3 only

While a `refname` pattern is allowed not to match any references, a non-pattern that doesn't resolve to a reference is invalid.

If a `refname` starts with minus (`-`) then it is treated as an exclusion filter – any references that it matches are excluded from the set included by the preceding filters (or the default set). For example:

    .../foo.git#v*,-v1.*  - exclude v1.* from v*
    .../foo.git##-v1.*    - exclude v1.* from default set

To support specifying literal leading minus, a `refname` that starts with plus (`+`) is treated as an inclusion filter. For example:

    .../foo.git#+x   - include  x
    .../foo.git#+-x  - include -x
    .../foo.git#++x  - include +x

Currently supported `git` protocols are `git://`, `ssh://` (but not `scp` pseudo-URL syntax), `http://`, and `https://` for remote repositories and `file://` for local repositories. While `bpkg` tries to minimize the amount of information (history) fetched, it is not always possible for some protocols and/or server configurations, as discussed next.

A `git` repository accessible via `http(s)://` can use either dumb or smart protocol (refer to the `git` documentation for details). The dumb protocol provides only limited support for fetch minimization and if this protocol is used, then `bpkg` has no choice but to download a substantial amount of history.

The smart protocol allows fetching of minimal history for tags and branches. Whether this is also possible for (all) commit ids depends on whether the server is configured to allow fetching unadvertised commits. For details, refer to the `uploadpack.allowReachableSHA1InWant` and `uploadpack.allowAnySHA1InWant` `git` configuration values.

The `git://` and `ssh://` protocols are similar to smart `http://` in that they support fetching minimal history for tags and branches and may or may not support this for commit ids depending on the server configuration. Note, however, that unlike for `http(s)://`, for these protocols `bpkg` does not try to sense if fetching unadvertised commits is allowed and always assumes that it is not. Also note that the sensed or assumed protocol capabilities can be overridden for a `git` repository URL prefix using the `--git-capabilities` option (`bpkg-common-options(1)`).

Based on this information, to achieve optimal results the recommended protocol for remote repositories is smart `https://`. Additionally, if you are planning to refer to unadvertised commit ids, then also consider configuring the server to allow fetching unadvertised commits.

The `file://` protocol has the same fetch minimization support as `git://` and is therefore treated the same.

# BUGS

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