Generating diff text
~~~~~~~~~~~~~~~~~~~~
-The attribute `diff` affects if 'git-diff' generates textual
-patch for the path or just says `Binary files differ`. It also
-can affect what line is shown on the hunk header `@@ -k,l +n,m @@`
-line.
+The attribute `diff` affects how 'git' generates diffs for particular
+files. It can tell git whether to generate a textual patch for the path
+or to treat the path as a binary file. It can also affect what line is
+shown on the hunk header `@@ -k,l +n,m @@` line, tell git to use an
+external command to generate the diff, or ask git to convert binary
+files to a text format before generating the diff.
Set::
Unset::
A path to which the `diff` attribute is unset will
- generate `Binary files differ`.
+ generate `Binary files differ` (or a binary patch, if
+ binary patches are enabled).
Unspecified::
String::
- Diff is shown using the specified custom diff driver.
- The driver program is given its input using the same
- calling convention as used for GIT_EXTERNAL_DIFF
- program. This name is also used for custom hunk header
- selection.
+ Diff is shown using the specified diff driver. Each driver may
+ specify one or more options, as described in the following
+ section. The options for the diff driver "foo" are defined
+ by the configuration variables in the "diff.foo" section of the
+ git config file.
-Defining a custom diff driver
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+Defining an external diff driver
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
The definition of a diff driver is done in `gitconfig`, not
`gitattributes` file, so strictly speaking this manual page is a
wrong place to talk about it. However...
-To define a custom diff driver `jcdiff`, add a section to your
+To define an external diff driver `jcdiff`, add a section to your
`$GIT_DIR/config` file (or `$HOME/.gitconfig` file) like this:
----------------------------------------------------------------
Defining a custom hunk-header
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-Each group of changes (called "hunk") in the textual diff output
+Each group of changes (called a "hunk") in the textual diff output
is prefixed with a line of the form:
@@ -k,l +n,m @@ TEXT
-The text is called 'hunk header', and by default a line that
-begins with an alphabet, an underscore or a dollar sign is used,
-which matches what GNU 'diff -p' output uses. This default
-selection however is not suited for some contents, and you can
-use customized pattern to make a selection.
+This is called a 'hunk header'. The "TEXT" portion is by default a line
+that begins with an alphabet, an underscore or a dollar sign; this
+matches what GNU 'diff -p' output uses. This default selection however
+is not suited for some contents, and you can use a customized pattern
+to make a selection.
-First in .gitattributes, you would assign the `diff` attribute
+First, in .gitattributes, you would assign the `diff` attribute
for paths.
------------------------
*.tex diff=tex
------------------------
-Then, you would define "diff.tex.funcname" configuration to
+Then, you would define a "diff.tex.xfuncname" configuration to
specify a regular expression that matches a line that you would
-want to appear as the hunk header, like this:
+want to appear as the hunk header "TEXT", like this:
------------------------
[diff "tex"]
- funcname = "^\\(\\\\\\(sub\\)*section{.*\\)$"
+ xfuncname = "^(\\\\(sub)*section\\{.*)$"
------------------------
Note. A single level of backslashes are eaten by the
- `html` suitable for HTML/XHTML documents.
-- `java` suitable for source code in the Java lanugage.
+- `java` suitable for source code in the Java language.
+
+- `objc` suitable for source code in the Objective-C language.
- `pascal` suitable for source code in the Pascal/Delphi language.
- `tex` suitable for source code for LaTeX documents.
+Performing text diffs of binary files
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Sometimes it is desirable to see the diff of a text-converted
+version of some binary files. For example, a word processor
+document can be converted to an ASCII text representation, and
+the diff of the text shown. Even though this conversion loses
+some information, the resulting diff is useful for human
+viewing (but cannot be applied directly).
+
+The `textconv` config option is used to define a program for
+performing such a conversion. The program should take a single
+argument, the name of a file to convert, and produce the
+resulting text on stdout.
+
+For example, to show the diff of the exif information of a
+file instead of the binary information (assuming you have the
+exif tool installed):
+
+------------------------
+[diff "jpg"]
+ textconv = exif
+------------------------
+
+NOTE: The text conversion is generally a one-way conversion;
+in this example, we lose the actual image contents and focus
+just on the text data. This means that diffs generated by
+textconv are _not_ suitable for applying. For this reason,
+only `git diff` and the `git log` family of commands (i.e.,
+log, whatchanged, show) will perform text conversion. `git
+format-patch` will never generate this output. If you want to
+send somebody a text-converted diff of a binary file (e.g.,
+because it quickly conveys the changes you have made), you
+should generate it separately and send it as a comment _in
+addition to_ the usual binary diff that you might send.
+
+
Performing a three-way merge
~~~~~~~~~~~~~~~~~~~~~~~~~~~~