Re: [PATCH] Improve the "diff --git" format documentation

From

AGAndreas Gruenbacher <agruen@suse.de>

Date

Oct 14, 2010, 10:53 UTC

Message-ID

<201010141253.11640.agruen@suse.de>

In-Reply-To

<7v8w21fsgr.fsf@alter.siamese.dyndns.org>

On Thursday 14 October 2010 03:55:48 Junio C Hamano wrote:

> [some more objections]

Andreas

--

[PATCH] Clarify and extend the "git diff" format documentation

Signed-off-by: Andreas Gruenbacher <agruen@suse.de>
---
 Documentation/diff-generate-patch.txt |   40 ++++++++++++++++++++++++--------
 1 files changed, 30 insertions(+), 10 deletions(-)

diff --git a/Documentation/diff-generate-patch.txt b/Documentation/diff-
generate-patch.txt
index 8f9a241..3ac2bea 100644
--- a/Documentation/diff-generate-patch.txt
+++ b/Documentation/diff-generate-patch.txt
@@ -9,16 +9,15 @@ patch file.  You can customize the creation of such patches 
via the
 GIT_EXTERNAL_DIFF and the GIT_DIFF_OPTS environment variables.
 
 What the -p option produces is slightly different from the traditional
-diff format.
+diff format:
 
-1.   It is preceded with a "git diff" header, that looks like
-     this:
+1.   It is preceded with a "git diff" header that looks like this:
 
        diff --git a/file1 b/file2
 +
 The `a/` and `b/` filenames are the same unless rename/copy is
 involved.  Especially, even for a creation or a deletion,
-`/dev/null` is _not_ used in place of `a/` or `b/` filenames.
+`/dev/null` is _not_ used in place of the `a/` or `b/` filenames.
 +
 When rename/copy is involved, `file1` and `file2` show the
 name of the source file of the rename/copy and the name of
@@ -37,18 +36,39 @@ the file that rename/copy produces, respectively.
        similarity index <number>
        dissimilarity index <number>
        index <hash>..<hash> <mode>
-
-3.  TAB, LF, double quote and backslash characters in pathnames
-    are represented as `\t`, `\n`, `\"` and `\\`, respectively.
-    If there is need for such substitution then the whole
-    pathname is put in double quotes.
-
++
+File modes are printed as 6-digit octal numbers including the file type
+and file permission bits.
++
+Path names in extended headers do not include the `a/` and `b/` prefixes.
++
 The similarity index is the percentage of unchanged lines, and
 the dissimilarity index is the percentage of changed lines.  It
 is a rounded down integer, followed by a percent sign.  The
 similarity index value of 100% is thus reserved for two equal
 files, while 100% dissimilarity means that no line from the old
 file made it into the new one.
++
+The index line includes the SHA-1 checksum before and after the change.
+The <mode> is included if the file mode does not change; otherwise,
+separate lines indicate the old and the new mode.
+
+3.  TAB, LF, double quote and backslash characters in pathnames
+    are represented as `\t`, `\n`, `\"` and `\\`, respectively.
+    If there is need for such substitution then the whole
+    pathname is put in double quotes.
+
+4.  All the `file1` files in the output refer to files before the
+    commit, and all the `file2` files refer to files after the commit.
+    It is incorrect to apply each change to each file sequentially.  For
+    example, this patch will swap a and b:
+
+      diff --git a/a b/b
+      rename from a
+      rename to b
+      diff --git a/b b/a
+      rename from b
+      rename to a
 
 
 combined diff format