`$(prefix)/etc/gitattributes` file.
Sometimes you would need to override an setting of an attribute
-for a path to `unspecified` state. This can be done by listing
+for a path to `Unspecified` state. This can be done by listing
the name of the attribute prefixed with an exclamation point `!`.
manually with `git update-ref -d refs/notes/textconv/jpg` (where
"jpg" is the name of the diff driver, as in the example above).
+Choosing textconv versus external diff
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+If you want to show differences between binary or specially-formatted
+blobs in your repository, you can choose to use either an external diff
+command, or to use textconv to convert them to a diff-able text format.
+Which method you choose depends on your exact situation.
+
+The advantage of using an external diff command is flexibility. You are
+not bound to find line-oriented changes, nor is it necessary for the
+output to resemble unified diff. You are free to locate and report
+changes in the most appropriate way for your data format.
+
+A textconv, by comparison, is much more limiting. You provide a
+transformation of the data into a line-oriented text format, and git
+uses its regular diff tools to generate the output. There are several
+advantages to choosing this method:
+
+1. Ease of use. It is often much simpler to write a binary to text
+ transformation than it is to perform your own diff. In many cases,
+ existing programs can be used as textconv filters (e.g., exif,
+ odt2txt).
+
+2. Git diff features. By performing only the transformation step
+ yourself, you can still utilize many of git's diff features,
+ including colorization, word-diff, and combined diffs for merges.
+
+3. Caching. Textconv caching can speed up repeated diffs, such as those
+ you might trigger by running `git log -p`.
+
+
Marking files as binary
^^^^^^^^^^^^^^^^^^^^^^^
`merge`
^^^^^^^
-The attribute `merge` affects how three versions of a file is
+The attribute `merge` affects how three versions of a file are
merged when a file-level merge is necessary during `git merge`,
and other commands such as `git revert` and `git cherry-pick`.
Take the version from the current branch as the
tentative merge result, and declare that the merge has
- conflicts. This is suitable for binary files that does
+ conflicts. This is suitable for binary files that do
not have a well-defined merge semantics.
Unspecified::
By default, this uses the same built-in 3-way merge
- driver as is the case the `merge` attribute is set.
- However, `merge.default` configuration variable can name
- different merge driver to be used for paths to which the
+ driver as is the case when the `merge` attribute is set.
+ However, the `merge.default` configuration variable can name
+ different merge driver to be used with paths for which the
`merge` attribute is unspecified.
String::
(See linkgit:git-config[1]).
-USING ATTRIBUTE MACROS
+USING MACRO ATTRIBUTES
----------------------
You do not want any end-of-line conversions applied to, nor textual diffs
------------
but that may become cumbersome, when you have many attributes. Using
-attribute macros, you can specify groups of attributes set or unset at
-the same time. The system knows a built-in attribute macro, `binary`:
+macro attributes, you can define an attribute that, when set, also
+sets or unsets a number of other attributes at the same time. The
+system knows a built-in macro attribute, `binary`:
------------
*.jpg binary
------------
-which is equivalent to the above. Note that the attribute macros can only
-be "Set" (see the above example that sets "binary" macro as if it were an
-ordinary attribute --- setting it in turn unsets "text" and "diff").
+Setting the "binary" attribute also unsets the "text" and "diff"
+attributes as above. Note that macro attributes can only be "Set",
+though setting one might have the effect of setting or unsetting other
+attributes or even returning other attributes to the "Unspecified"
+state.
-DEFINING ATTRIBUTE MACROS
+DEFINING MACRO ATTRIBUTES
-------------------------
-Custom attribute macros can be defined only in the `.gitattributes` file
-at the toplevel (i.e. not in any subdirectory). The built-in attribute
-macro "binary" is equivalent to:
+Custom macro attributes can be defined only in the `.gitattributes`
+file at the toplevel (i.e. not in any subdirectory). The built-in
+macro attribute "binary" is equivalent to:
------------
[attr]binary -diff -text