spaces in their name, or early termination of fast-import when it encounters
unexpected input.
+Stream Comments
+~~~~~~~~~~~~~~~
+To aid in debugging frontends fast-import ignores any line that
+begins with `#` (ASCII pound/hash) up to and including the line
+ending `LF`. A comment line may contain any sequence of bytes
+that does not contain an LF and therefore may be used to include
+any detailed debugging information that might be specific to the
+frontend and useful when inspecting a fast-import data stream.
+
Date Formats
~~~~~~~~~~~~
The following date formats are supported. A frontend should select
This command is optional and is not needed to perform
an import.
+`progress`::
+ Causes fast-import to echo the entire line to its own
+ standard output. This command is optional and is not needed
+ to perform an import.
+
`commit`
~~~~~~~~
Create or update a branch with a new commit, recording one logical
('from' SP <committish> LF)?
('merge' SP <committish> LF)?
(filemodify | filedelete | filecopy | filerename | filedeleteall)*
- LF
+ LF?
....
where `<ref>` is the name of the branch to make the commit on.
commit, as `filedeleteall`
wipes the branch clean (see below).
+The `LF` after the command is optional (it used to be required).
+
`author`
^^^^^^^^
An `author` command may optionally appear, if the author information
....
'reset' SP <ref> LF
('from' SP <committish> LF)?
- LF
+ LF?
....
For a detailed description of `<ref>` and `<committish>` see above
under `commit` and `from`.
+The `LF` after the command is optional (it used to be required).
+
The `reset` command can also be used to create lightweight
(non-annotated) tags. For example:
exact byte count format, as it is more robust and performs better.
The delimited format is intended primarily for testing fast-import.
+Comment lines appearing within the `<raw>` part of `data` commands
+are always taken to be part of the body of the data and are therefore
+never ignored by fast-import. This makes it safe to import any
+file/message content whose lines might start with `#`.
+
Exact byte count format::
The frontend must specify the number of bytes of data.
+
....
'data' SP <count> LF
- <raw> LF
+ <raw> LF?
....
+
where `<count>` is the exact number of bytes appearing within
`<raw>`. The value of `<count>` is expressed as an ASCII decimal
integer. The `LF` on either side of `<raw>` is not
included in `<count>` and will not be included in the imported data.
++
+The `LF` after `<raw>` is optional (it used to be required) but
+recommended. Always including it makes debugging a fast-import
+stream easier as the next command always starts in column 0
+of the next line, even if `<raw>` did not end with an `LF`.
Delimited format::
A delimiter string is used to mark the end of the data.
'data' SP '<<' <delim> LF
<raw> LF
<delim> LF
+ LF?
....
+
where `<delim>` is the chosen delimiter string. The string `<delim>`
immediately trailing `<raw>` is part of `<raw>`. This is one of
the limitations of the delimited format, it is impossible to supply
a data chunk which does not have an LF as its last byte.
++
+The `LF` after `<delim> LF` is optional (it used to be required).
`checkpoint`
~~~~~~~~~~~~
....
'checkpoint' LF
- LF
+ LF?
....
Note that fast-import automatically switches packfiles when the current
repository can be loaded into Git through fast-import in about 3 hours,
explicit checkpointing may not be necessary.
+The `LF` after the command is optional (it used to be required).
+
+`progress`
+~~~~~~~~~~
+Causes fast-import to print the entire `progress` line unmodified to
+its standard output channel (file descriptor 1) when the command is
+processed from the input stream. The command otherwise has no impact
+on the current import, or on any of fast-import's internal state.
+
+....
+ 'progress' SP <any> LF
+ LF?
+....
+
+The `<any>` part of the command may contain any sequence of bytes
+that does not contain `LF`. The `LF` after the command is optional.
+Callers may wish to process the output through a tool such as sed to
+remove the leading part of the line, for example:
+
+====
+ frontend | git-fast-import | sed 's/^progress //'
+====
+
+Placing a `progress` command immediately after a `checkpoint` will
+inform the reader when the `checkpoint` has been completed and it
+can safely access the refs that fast-import updated.
Tips and Tricks
---------------
You only need to expend the effort once, and everyone using your
project will benefit from the smaller repository.
+Include Some Progress Messages
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Every once in a while have your frontend emit a `progress` message
+to fast-import. The contents of the messages are entirely free-form,
+so one suggestion would be to output the current month and year
+each time the current commit date moves into the next month.
+Your users will feel better knowing how much of the data stream
+has been processed.
+
Packfile Optimization
---------------------