See ``Date Formats'' below for details about which formats
are supported, and their syntax.
+-- done::
+ Terminate with error if there is no 'done' command at the
+ end of the stream.
+
--force::
Force updating modified existing branches, even if doing
so would cause commits to be lost (as the new commit does
options.
--cat-blob-fd=<fd>::
- Specify the file descriptor that will be written to
- when the `cat-blob` command is encountered in the stream.
- The default behaviour is to write to `stdout`.
+ Write responses to `cat-blob` and `ls` queries to the
+ file descriptor <fd> instead of `stdout`. Allows `progress`
+ output intended for the end-user to be separated from other
+ output.
--done::
Require a `done` command at the end of the stream.
----
from refs/heads/branch^0
----
-The `{caret}0` suffix is necessary as fast-import does not permit a branch to
+The `^0` suffix is necessary as fast-import does not permit a branch to
start from itself, and the branch is created in memory before the
-`from` command is even read from the input. Adding `{caret}0` will force
+`from` command is even read from the input. Adding `^0` will force
fast-import to resolve the commit through Git's revision parsing library,
rather than its internal branch table, thereby loading in the
existing value of the branch.
accepted. In particular, the `cat-blob` command can be used in the
middle of a commit but not in the middle of a `data` command.
+See ``Responses To Commands'' below for details about how to read
+this output safely.
+
`ls`
~~~~
Prints information about the object at a path to a file descriptor
See `filemodify` above for a detailed description of `<path>`.
-Output uses the same format as `git ls-tree <tree>
{litdd} <path>`:
+Output uses the same format as `git ls-tree <tree>
-- <path>`:
====
<mode> SP ('blob' | 'tree' | 'commit') SP <dataref> HT <path> LF
missing SP <path> LF
====
+See ``Responses To Commands'' below for details about how to read
+this output safely.
+
`feature`
~~~~~~~~~
Require that fast-import supports the specified feature, or abort if
Error out if the stream ends without a 'done' command.
Without this feature, errors causing the frontend to end
abruptly at a convenient point in the stream can go
- undetected.
+ undetected. This may occur, for example, if an import
+ front end dies in mid-operation without emitting SIGTERM
+ or SIGKILL at its subordinate git fast-import instance.
`option`
~~~~~~~~
in use, the `done` command is mandatory and marks the end of the
stream.
+Responses To Commands
+---------------------
+New objects written by fast-import are not available immediately.
+Most fast-import commands have no visible effect until the next
+checkpoint (or completion). The frontend can send commands to
+fill fast-import's input pipe without worrying about how quickly
+they will take effect, which improves performance by simplifying
+scheduling.
+
+For some frontends, though, it is useful to be able to read back
+data from the current repository as it is being updated (for
+example when the source material describes objects in terms of
+patches to be applied to previously imported objects). This can
+be accomplished by connecting the frontend and fast-import via
+bidirectional pipes:
+
+====
+ mkfifo fast-import-output
+ frontend <fast-import-output |
+ git fast-import >fast-import-output
+====
+
+A frontend set up this way can use `progress`, `ls`, and `cat-blob`
+commands to read information from the import in progress.
+
+To avoid deadlock, such frontends must completely consume any
+pending output from `progress`, `ls`, and `cat-blob` before
+performing writes to fast-import that might block.
+
Crash Reports
-------------
If fast-import is supplied invalid input it will terminate with a