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+*diff.txt*      For Vim version 7.0aa.  Last change: 2004 May 01
+
+
+		  VIM REFERENCE MANUAL    by Bram Moolenaar
+
+
+				*diff* *vimdiff* *gvimdiff* *diff-mode*
+This file describes the +diff feature: Showing differences between two or
+three versions of the same file.
+
+The basics are explained in section |08.7| of the user manual.
+
+1. Starting diff mode		|vimdiff|
+2. Viewing diffs		|view-diffs|
+3. Jumping to diffs		|jumpto-diffs|
+4. Copying diffs		|copy-diffs|
+5. Diff options			|diff-options|
+
+{not in Vi}
+
+==============================================================================
+1. Starting diff mode
+
+The easiest way to start editing in diff mode is with the "vimdiff" command.
+This starts Vim as usual, and additionally sets up for viewing the differences
+between the arguments. >
+
+	vimdiff file1 file2 [file3 [file4]]
+
+This is equivalent to: >
+
+	vim -d file1 file2 [file3 [file4]]
+
+You may also use "gvimdiff" or "vim -d -g".  The GUI is started then.
+You may also use "viewdiff" or "gviewdiff".  Vim starts in readonly mode then.
+"r" may be prepended for restricted mode (see |-Z|).
+
+The second and following arguments may also be a directory name.  Vim will
+then append the file name of the first argument to the directory name to find
+the file.
+
+This only works when a standard "diff" command is available.  See 'diffexpr'.
+
+What happens is that Vim opens a window for each of the files.  This is like
+using the |-O| argument.  This uses vertical splits.  If you prefer horizontal
+splits add the |-o| argument: >
+
+	vimdiff -o file1 file2 [file3]
+
+In each of the edited files these options are set:
+
+	'diff'		on
+	'scrollbind'	on
+	'scrollopt'	includes "hor"
+	'wrap'		off
+	'foldmethod'	"diff"
+	'foldcolumn'	2
+
+These options are set local to the window.  When editing another file they are
+reset to the global value.
+
+The differences shown are actually the differences in the buffer.  Thus if you
+make changes after loading a file, these will be included in the displayed
+diffs.  You might have to do ":diffupdate" now and then, not all changes are
+immediately taken into account.
+
+In your .vimrc file you could do something special when Vim was started in
+diff mode.  You could use a construct like this: >
+
+	if &diff
+	   setup for diff mode
+	else
+	   setup for non-diff mode
+	endif
+
+While already in Vim you can start diff mode in three ways.
+
+							*E98*
+:diffsplit {filename}					*:diffs* *:diffsplit*
+		Open a new window on the file {filename}.  The options are set
+		as for "vimdiff" for the current and the newly opened window.
+		Also see 'diffexpr'.
+
+							*:difft* *:diffthis*
+:diffthis	Make the current window part of the diff windows.  This sets
+		the option like for "vimdiff".
+
+:diffpatch {patchfile}					*:diffp* *:diffpatch*
+		Use the current buffer, patch it with the diff found in
+		{patchfile} and open a buffer on the result.  The options are
+		set as for "vimdiff".
+		{patchfile} can be in any format that the "patch" program
+		understands or 'patchexpr' can handle.
+		Note that {patchfile} should only contain a diff for one file,
+		the current file.  If {patchfile} contains diffs for other
+		files as well, the results are unpredictable.  Vim changes
+		directory to /tmp to avoid files in the current directory
+		accidentally being patched.  But it may still result in
+		various ".rej" files to be created.  And when absolute path
+		names are present these files may get patched anyway.
+
+To make these commands use a vertical split, prepend |:vertical|.  Examples: >
+
+	:vert diffsplit main.c~
+	:vert diffpatch /tmp/diff
+<
+							*E96*
+There can be up to four buffers with 'diff' set.
+
+Since the option values are remembered with the buffer, you can edit another
+file for a moment and come back to the same file and be in diff mode again.
+If you don't want diff mode, reset the 'diff' option.  And you probably want
+to get rid of the fold column: >
+
+	:set nodiff foldcolumn=0
+
+==============================================================================
+2. Viewing diffs						*view-diffs*
+
+The effect is that the diff windows show the same text, with the differences
+highlighted.  When scrolling the text, the 'scrollbind' option will make the
+text in other windows to be scrolled as well.  With vertical splits the text
+should be aligned properly.
+
+The alignment of text will go wrong when:
+- 'wrap' is on, some lines will be wrapped and occupy two or more screen
+  lines
+- folds are open in one window but not another
+- 'scrollbind' is off
+- changes have been made to the text
+- "filler" is not present in 'diffopt', deleted/inserted lines makes the
+  alignment go wrong
+
+All the buffers edited in a window where the 'diff' option is set will join in
+the diff.  This is also possible for hidden buffers.  They must have been
+edited in a window first for this to be possible.
+
+Since 'diff' is a window-local option, it's possible to view the same buffer
+in diff mode in one window and "normal" in another window.  It is also
+possible to view the changes you have made to a buffer, but since Vim doesn't
+allow having two buffers for the same file, you need to make a copy of the
+original file and diff with that.  For example: >
+	:!cp % tempfile
+	:diffsplit tempfile
+
+A buffer that is unloaded cannot be used for the diff.  But it does work for
+hidden buffers.  You can use ":hide" to close a window without unloading the
+buffer.
+
+
+							*:diffu* *:diffupdate*
+Vim attempts to keep the differences updated when you make changes to the
+text.  This mostly takes care of inserted and deleted lines.  Changes within a
+line and more complicated changes do not cause the differences to be updated.
+To force the differences to be updated use: >
+
+	:diffupdate
+
+
+Vim will show filler lines for lines that are missing in one window but are
+present in another.  These lines were inserted in another file or deleted in
+this file.  Removing "filler" from the 'diffopt' option will make Vim not
+display these filler lines.
+
+
+Folds are used to hide the text that wasn't changed.  See |folding| for all
+the commands that can be used with folds.
+
+The context of lines above a difference that are not included in the fold can
+be set with the 'diffopt' option.  For example, to set the context to three
+lines: >
+
+	:set diffopt=filler,context:3
+
+
+The diffs are highlighted with these groups:
+
+|hl-DiffAdd|	DiffAdd		Added (inserted) lines.  These lines exist in
+				this buffer but not in another.
+|hl-DiffChange|	DiffChange	Changed lines.
+|hl-DiffText|	DiffText	Changed text inside a Changed line.  Vim
+				finds the first character that is different,
+				and the last character that is different
+				(searching from the end of the line).  The
+				text in between is highlighted.  This means
+				that parts in the middle that are still the
+				same are highlighted anyway.
+|hl-DiffDelete| DiffDelete	Deleted lines.  Also called filler lines,
+				because they don't really exist in this
+				buffer.
+
+==============================================================================
+3. Jumping to diffs					*jumpto-diffs*
+
+Two commands can be used to jump to diffs:
+								*[c*
+	[c		Jump backwards to the previous start of a change.
+			When a count is used, do it that many times.
+								*]c*
+	]c		Jump forwards to the next start of a change.
+			When a count is used, do it that many times.
+
+It is an error if there is no change for the cursor to move to.
+
+==============================================================================
+4. Diff copying			*copy-diffs* *E99* *E100* *E101* *E102* *E103*
+
+There are two commands to copy text from one buffer to another.  The result is
+that the buffers will be equal within the specified range.
+
+							*:diffg* *:diffget*
+:[range]diffg[et] [bufspec]
+		Modify the current buffer to undo difference with another
+		buffer.  If [bufspec] is given, that buffer is used.
+		Otherwise this only works if there is one other buffer in diff
+		mode.
+		See below for [range].
+
+							*:diffpu* *:diffput*
+:[range]diffpu[t] [bufspec]
+		Modify another buffer to undo difference with the current
+		buffer.  Just like ":diffget" but the other buffer is modified
+		instead of the current one.
+		See below for [range].
+
+							*do*
+do		Same as ":diffget" without argument or range.  The "o" stands
+		for "obtain" ("dg" can't be used, it could be the start of
+		"dgg"!).
+
+							*dp*
+dp		Same as ":diffput" without argument or range.
+
+When no [range] is given, the diff at the cursor position or just above it is
+affected.  When [range] is used, Vim tries to only put or get the specified
+lines.  When there are deleted lines, this may not always be possible.
+
+There can be deleted lines below the last line of the buffer.  When the cursor
+is on the last line in the buffer and there is no diff above this line, the
+":diffget" and "do" commands will obtain lines from the other buffer.
+
+To be able to get those lines from another buffer in a [range] it's allowed to
+use the last line number plus one.  This command gets all diffs from the other
+buffer: >
+
+	:1,$+1diffget
+
+Note that deleted lines are displayed, but not counted as text lines.  You
+can't move the cursor into them.  To fill the deleted lines with the lines
+from another buffer use ":diffget" on the line below them.
+
+The [bufspec] argument above can be a buffer number, a pattern for a buffer
+name or a part of a buffer name.  Examples:
+
+	:diffget		Use the other buffer which is in diff mode
+	:diffget 3		Use buffer 3
+	:diffget v2		Use the buffer which matches "v2" and is in
+				diff mode (e.g., "file.c.v2")
+
+==============================================================================
+5. Diff options						*diff-options*
+
+Also see |'diffopt'| and the "diff" item of |'fillchars'|.
+
+
+FINDING THE DIFFERENCES					*diff-diffexpr*
+
+The 'diffexpr' option can be set to use something else than the standard
+"diff" program to compare two files and find the differences.
+
+When 'diffexpr' is empty, Vim uses this command to find the differences
+between file1 and file2: >
+
+	diff file1 file2 > outfile
+
+The ">" is replaced with the value of 'shellredir'.
+
+The output of "diff" must be a normal "ed" style diff.  Do NOT use a context
+diff.  This example explains the format that Vim expects: >
+
+	1a2
+	> bbb
+	4d4
+	< 111
+	7c7
+	< GGG
+	---
+	> ggg
+
+The "1a2" item appends the line "bbb".
+The "4d4" item deletes the line "111".
+The '7c7" item replaces the line "GGG" with "ggg".
+
+When 'diffexpr' is not empty, Vim evaluates to obtain a diff file in the
+format mentioned.  These variables are set to the file names used:
+
+	v:fname_in		original file
+	v:fname_new		new version of the same file
+	v:fname_out		resulting diff file
+
+Additionally, 'diffexpr' should take care of "icase" and "iwhite" in the
+'diffopt' option.  'diffexpr' cannot change the value of 'lines' and
+'columns'.
+
+Example (this does almost the same as 'diffexpr' being empty): >
+
+	set diffexpr=MyDiff()
+	function MyDiff()
+	   let opt = ""
+	   if &diffopt =~ "icase"
+	     let opt = opt . "-i "
+	   endif
+	   if &diffopt =~ "iwhite"
+	     let opt = opt . "-b "
+	   endif
+	   silent execute "!diff -a --binary " . opt . v:fname_in . " " . v:fname_new .
+		\  " > " . v:fname_out
+	endfunction
+
+The "-a" argument is used to force comparing the files as text, comparing as
+binaries isn't useful.  The "--binary" argument makes the files read in binary
+mode, so that a CTRL-Z doesn't end the text on DOS.
+
+						*E97*
+Vim will do a test if the diff output looks alright.  If it doesn't, you will
+get an error message.  Possible causes:
+-  The "diff" program cannot be executed.
+-  The "diff" program doesn't produce normal "ed" style diffs (see above).
+-  The 'shell' and associated options are not set correctly.  Try if filtering
+   works with a command like ":!sort".
+-  You are using 'diffexpr' and it doesn't work.
+If it's not clear what the problem is set the 'verbose' option to see more
+messages.
+
+
+USING PATCHES					*diff-patchexpr*
+
+The 'patchexpr' option can be set to use something else than the standard
+"patch" program.
+
+When 'patchexpr' is empty, Vim will call the "patch" program like this: >
+
+	patch -o outfile origfile < patchfile
+
+This should work fine with most versions of the "patch" program.  Note that a
+CR in the middle of a line may cause problems, it is seen as a line break.
+
+If the default doesn't work for you, set the 'patchexpr' to an expression that
+will have the same effect.  These variables are set to the file names used:
+
+	v:fname_in		original file
+	v:fname_diff		patch file
+	v:fname_out		resulting patched file
+
+Example (this does the same as 'patchexpr' being empty): >
+
+	let patchexpr=MyPatch
+	function MyPatch
+	   :call system("patch -o " . v:fname_out . " " . v:fname_in .
+	   \  " < " . v:fname_diff)
+	endfunction
+
+Make sure that using the "patch" program doesn't have unwanted side effects.
+For example, watch out for additionally generated files, which should be
+deleted.  It should just patch the file and nothing else.
+   Vim will change directory to "/tmp" or another temp directory before
+evaluating 'patchexpr'.  This hopefully avoids that files in the current
+directory are accidentally patched.  Vim will also delete files starting with
+v:fname_in and ending in ".rej" and ".orig".
+
+ vim:tw=78:ts=8:ft=help:norl: