359 lines
12 KiB
Markdown
359 lines
12 KiB
Markdown
# Git LFS API
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The server implements a simple API for uploading and downloading binary content.
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Git repositories that use Git LFS will specify a URI endpoint. See the
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[specification](spec.md) for how Git LFS determines the server endpoint to use.
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Use that endpoint as a base, and append the following relative paths to upload
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and download from the Git LFS server.
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API requests require an Accept header of `application/vnd.git-lfs+json`. The
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upload and verify requests need a `application/vnd.git-lfs+json` Content-Type
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too.
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## Authentication
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The Git LFS API uses [git credentials](http://git-scm.com/docs/gitcredentials) to
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access the API username and password. If the Git LFS domain matches the Git
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remote's, Git LFS will not prompt you again to enter the password.
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If the Git remote is using SSH, Git LFS will execute the `git-lfs-authenticate`
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command. It passes the SSH path, the Git LFS operation (upload or download),
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and the object OID as arguments. A successful result outputs a JSON link object
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to STDOUT. This is applied to any Git LFS API request before git credentials
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are accessed.
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```
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# remote: git@github.com:user/repo.git
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$ ssh git@github.com git-lfs-authenticate user/repo.git download {oid}
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{
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"header": {
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"Authorization": "Basic ..."
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}
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// OPTIONAL key only needed if the Git LFS server is not hosted at the default
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// URL from the Git remote:
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// https://github.com/user/repo.git/info/lfs
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"href": "https://other-server.com/user/repo",
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}
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```
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If Git LFS detects a non-zero exit status, it displays the command's STDERR:
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```
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$ ssh git@github.com git-lfs-authenticate user/repo.git wat {oid}
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Invalid LFS operation: "wat"
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```
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NOTE: The Git LFS client currently does not cache the headers from the SSH
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command. This is being considered for a future release.
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## API Responses
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This specification defines what status codes that API can return. Look at each
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individual API method for more details. Some of the specific status codes may
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trigger specific error messages from the client.
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* 200 - The request completed successfully.
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* 202 - An upload request has been accepted. Clients must follow hypermedia
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links to actually upload the content.
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* 301 - A permanent redirect. Only supported for GET/HEAD requests.
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* 302 - A temporary redirect. Only supported for GET/HEAD requests.
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* 303 - A temporary redirect. Only supported for GET/HEAD requests.
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* 307 - A temporary redirect. Keeps the original request method intact.
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* 400 - General error with the client's request. Invalid JSON formatting, for
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example.
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* 401 - The authentication credentials are incorrect.
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* 403 - The requesting user has access to see the repository, but not to push
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changes to it.
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* 404 - Either the user does not have access to see the repository, or the
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repository or requested object does not exist.
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The following status codes can optionally be returned from the API, depending on
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the server implementation.
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* 406 - The Accept header needs to be `application/vnd.git-lfs+json`.
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* 410 - The requested object used to exist, but was deleted. The message should
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state why (user initiated, legal issues, etc).
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* 429 - The user has hit a rate limit with the server. Though the API does not
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specify any rate limits, implementors are encouraged to set some for
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availability reasons.
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* 501 - The server has not implemented the current method. Reserved for future
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use.
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* 509 - Returned if the bandwidth limit for the user or repository has been
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exceeded. The API does not specify any bandwidth limit, but implementors may
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track usage.
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Some server errors may trigger the client to retry requests, such as 500, 502,
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503, and 504.
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If the server returns a JSON error object, the client can display this message
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to users.
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```
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> GET https://git-lfs-server.com/objects/{OID} HTTP/1.1
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> Accept: application/vnd.git-lfs+json
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>
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< HTTP/1.1 200 OK
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< Content-Type: application/vnd.git-lfs+json
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<
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< {
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< "message": "Bad credentials",
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< "documentation_url": "https://git-lfs-server.com/docs/errors",
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< "request_id": "123"
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< }
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```
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The `documentation_url` and `request_id` properties are optional. If given,
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they are displayed to the user.
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## Redirections
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The Git LFS client follows redirections on the core Git LFS API methods only.
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Any of the hypermedia hrefs that are returned must be for the current location.
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The client will pass all of the original request headers to the redirected
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request, only changing the URL based on the redirect location. The only
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exception is the Authorization header, which is only passed through if the
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original request and the new location have a matching URL scheme, host, and
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port.
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The client will automatically follow redirections for GET or HEAD requests on
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a 301, 302, 303, or 307 HTTP status. It only automatically follows redirections
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for other HTTP verbs on a 307 HTTP status.
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Note: the 308 HTTP status is not official, and has conflicting proposals for its
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intended use. It is not supported as a redirection.
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## Hypermedia
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The Git LFS API uses hypermedia hints to instruct the client what to do next.
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These links are included in a `_links` property. Possible relations for objects
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include:
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* `self` - This points to the object's canonical API URL.
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* `download` - Follow this link with a GET and the optional header values to
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download the object content.
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* `upload` - Upload the object content to this link with a PUT.
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* `verify` - Optional link for the client to POST after an upload. If
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included, the client assumes this step is required after uploading an object.
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See the "Verification" section below for more.
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Link relations specify the `href`, and optionally a collection of header values
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to set for the request. These are optional, and depend on the backing object
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store that the Git LFS API is using.
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The Git LFS client will automatically send the same credentials to the followed
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link relation as Basic Authentication IF:
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* The url scheme, host, and port all match the Git LFS API endpoint's.
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* The link relation does not specify an Authorization header.
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If the host name is different, the Git LFS API needs to send enough information
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through the href query or header values to authenticate the request.
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The Git LFS client expects a 200 or 201 response from these hypermedia requests.
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Any other response code is treated as an error.
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## GET /objects/{oid}
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This gets the object's meta data. The OID is the value from the object pointer.
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```
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> GET https://git-lfs-server.com/objects/{OID} HTTP/1.1
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> Accept: application/vnd.git-lfs+json
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> Authorization: Basic ... (if authentication is needed)
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>
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< HTTP/1.1 200 OK
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< Content-Type: application/vnd.git-lfs+json
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<
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< {
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< "oid": "the-sha-256-signature",
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< "size": 123456,
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< "_links": {
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< "self": {
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< "href": "https://git-lfs-server.com/objects/OID",
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< },
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< "download": {
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< "href": "https://some-download.com",
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< "header": {
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< "Key": "value"
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< }
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< }
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< }
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< }
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```
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The `oid` and `size` properties are required. A hypermedia `_links` section is
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included with a `download` link relation. Clients can follow this link to
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access the object content. See the "Hypermedia" section above for more.
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Here's a sample response for a request with an authorization error:
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```
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> GET https://git-lfs-server.com/objects/{OID} HTTP/1.1
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> Accept: application/vnd.git-lfs+json
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> Authorization: Basic ... (if authentication is needed)
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>
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< HTTP/1.1 404 Not found
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< Content-Type: application/vnd.git-lfs+json
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<
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< {
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< "message": "Not found"
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< }
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```
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### Responses
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* 200 - The object exists and the user has access to download it.
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* 401 - The authentication credentials are incorrect.
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* 404 - The user does not have access to the object, or it does not exist.
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* 410 - The object used to exist, but was deleted. The message should state why
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(user initiated, legal issues, etc).
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## POST /objects
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This request initiates the upload of an object, given a JSON body with the oid
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and size of the object to upload.
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```
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> POST https://git-lfs-server.com/objects HTTP/1.1
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> Accept: application/vnd.git-lfs+json
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> Content-Type: application/vnd.git-lfs+json
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> Authorization: Basic ... (if authentication is needed)
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>
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> {
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> "oid": "1111111",
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> "size": 123
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> }
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>
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< HTTP/1.1 202 Accepted
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< Content-Type: application/vnd.git-lfs+json
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<
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< {
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< "_links": {
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< "upload": {
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< "href": "https://some-upload.com",
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< "header": {
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< "Key": "value"
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< }
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< },
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< "verify": {
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< "href": "https://some-callback.com",
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< "header": {
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< "Key": "value"
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< }
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< }
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< }
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< }
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```
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A response can include one of multiple link relations, each with an `href`
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property and an optional `header` property.
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* `upload` - This relation describes how to upload the object. Expect this with
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a 202 status.
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* `verify` - The server can specify a URL for the client to hit after
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successfully uploading an object. This is an optional relation for a 202
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status.
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* `download` - This relation describes how to download the object content. This
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only appears on a 200 status.
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### Responses
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* 200 - The object already exists. Don't bother re-uploading.
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* 202 - The object is ready to be uploaded. Follow the "upload" and optional
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"verify" links.
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* 401 - The authentication credentials are incorrect.
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* 403 - The user has **read**, but not **write** access.
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* 404 - The repository does not exist for the user.
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## POST /objects/batch
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This request retrieves the metadata for a batch of objects, given a JSON body
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containing an object with an array of objects with the oid and size of each object.
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NOTE: This is an experimental API that is subject to change. It will ship disabled
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by default in Git LFS v0.5.2. You can enable it if your Git LFS server supports it
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with `git config lfs.batch true`.
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```
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> POST https://git-lfs-server.com/objects/batch HTTP/1.1
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> Accept: application/vnd.git-lfs+json
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> Content-Type: application/vnd.git-lfs+json
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> Authorization: Basic ... (if authentication is needed)
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>
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> {
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> "objects": [
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> {
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> "oid": "1111111",
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> "size": 123
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> }
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> ]
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> }
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>
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< HTTP/1.1 200 Accepted
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< Content-Type: application/vnd.git-lfs+json
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<
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< {
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< "objects": [
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< {
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< "oid": "1111111",
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< "_links": {
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< "upload": {
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< "href": "https://some-upload.com",
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< "header": {
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< "Key": "value"
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< }
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< },
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< "verify": {
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< "href": "https://some-callback.com",
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< "header": {
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< "Key": "value"
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< }
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< }
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< }
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> }
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< ]
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< }
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```
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The response will be an object containing an array of objects with one of
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multiple link relations, each with an `href` property and an optional `header`
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property.
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* `upload` - This relation describes how to upload the object. Expect this with
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when the object has not been previously uploaded.
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* `verify` - The server can specify a URL for the client to hit after
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successfully uploading an object. This is an optional relation for the case that
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the server has not verified the object.
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* `download` - This relation describes how to download the object content. This
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only appears if an object has been previously uploaded.
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### Responses
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* 200 - OK
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* 401 - The authentication credentials are incorrect.
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* 403 - The user has **read**, but not **write** access.
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* 404 - The repository does not exist for the user.
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## Verification
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When Git LFS clients issue a POST request to initiate an object upload, the
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response can potentially return a "verify" link relation. If given, The Git LFS
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API expects a POST to the href after a successful upload. Git LFS clients send:
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* `oid` - The String OID of the Git LFS object.
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* `size` - The integer size of the Git LFS object, in bytes.
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```
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> POST https://git-lfs-server.com/callback
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> Accept: application/vnd.git-lfs+json
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> Content-Type: application/vnd.git-lfs+json
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> Content-Length: 123
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>
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> {"oid": "{oid}", "size": 10000}
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>
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< HTTP/1.1 200 OK
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```
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A 200 response means that the object exists on the server.
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