`filter`
^^^^^^^^
-A `filter` attribute can be set to a string value. This names
+A `filter` attribute can be set to a string value that names a
filter driver specified in the configuration.
-A filter driver consists of `clean` command and `smudge`
+A filter driver consists of a `clean` command and a `smudge`
command, either of which can be left unspecified. Upon
-checkout, when `smudge` command is specified, the command is fed
-the blob object from its standard input, and its standard output
-is used to update the worktree file. Similarly, `clean` command
-is used to convert the contents of worktree file upon checkin.
+checkout, when the `smudge` command is specified, the command is
+fed the blob object from its standard input, and its standard
+output is used to update the worktree file. Similarly, the
+`clean` command is used to convert the contents of worktree file
+upon checkin.
-Missing filter driver definition in the config is not an error
+A missing filter driver definition in the config is not an error
but makes the filter a no-op passthru.
The content filtering is done to massage the content into a
shape that is more convenient for the platform, filesystem, and
-the user to use. The keyword here is "more convenient" and not
-"turning something unusable into usable". In other words, it is
-"hanging yourself because we gave you a long rope" if your
-project uses filtering mechanism in such a way that it makes
-your project unusable unless the checkout is done with a
-specific filter in effect.
+the user to use. The key phrase here is "more convenient" and not
+"turning something unusable into usable". In other words, the
+intent is that if someone unsets the filter driver definition,
+or does not have the appropriate filter program, the project
+should still be usable.
Interaction between checkin/checkout attributes
----------------------------------------------------------------
+Creating an archive
+~~~~~~~~~~~~~~~~~~~
+
+`export-subst`
+^^^^^^^^^^^^^^
+
+If the attribute `export-subst` is set for a file then git will expand
+several placeholders when adding this file to an archive. The
+expansion depends on the availability of a commit ID, i.e. if
+gitlink:git-archive[1] has been given a tree instead of a commit or a
+tag then no replacement will be done. The placeholders are the same
+as those for the option `--pretty=format:` of gitlink:git-log[1],
+except that they need to be wrapped like this: `$Format:PLACEHOLDERS$`
+in the file. E.g. the string `$Format:%H$` will be replaced by the
+commit hash.
+
+
GIT
---
Part of the gitlink:git[7] suite