Re: [PATCH/RFC] diff --relative: output paths as relative to the current subdirectory

Junio C Hamano [off-list ref] writes:

Linus Torvalds [off-list ref] writes:

quoted

So I simply don't think that we should assume a working directory for any 
basic git operation, unless that operation fundamentally needs one because 
it's only defined for a system with working directories (which is fairly 
rare, but obviously happens: "git reset --hard", "git pull/merge", "git 
checkout" etc).

Yeah, but that begs for a larger design-level question.

Instead of treating "diff --relative=drivers/ a..b", as a
special case, shouldn't we have a more general "I may be in a
bare repository, but please pretend that my prefix were this
path" option?

    $ git --prefix=drivers/ diff --relative a..b -- scsi
    $ git --prefix=drivers/scsi log a..b .

Of course, if you are truly in a bare repository and if you did
an operation that wants a work tree, you would get mostly
useless results, e.g.

    $ git --prefix=fs/ diff v2.6.24 -- ext3

will give you tons of whole-file removals.

I suspect that a lot of existing code assumes a non NULL prefix
automatically means we have work tree, which needs to be fixed,
if we go this route, though.

This does not address the above issue, but simply adds the
special purpose --relative=<path>.

The earlier one had the option described only in "git-diff"
manual page, simply because I originally planned to do this only
for "git-diff" Porcelain and nothing else.  But it should have
been described as a general diff option.  This moves the
description where it belongs to.

Signed-off-by: Junio C Hamano <redacted>
---

 Documentation/diff-options.txt |    8 ++++++++
 Documentation/git-diff.txt     |    5 -----
 diff.c                         |    4 ++++
 revision.c                     |    2 +-
 4 files changed, 13 insertions(+), 6 deletions(-)

diff --git a/Documentation/diff-options.txt b/Documentation/diff-options.txt
index 8d35cbd..8dc5b00 100644
--- a/Documentation/diff-options.txt
+++ b/Documentation/diff-options.txt

@@ -170,6 +170,14 @@ endif::git-format-patch[]
 	Swap two inputs; that is, show differences from index or
 	on-disk file to tree contents.
 
+--relative[=<path>]::
+	When run from a subdirectory of the project, it can be
+	told to exclude changes outside the directory and show
+	pathnames relative to it with this option.  When you are
+	not in a subdirectory (e.g. in a bare repository), you
+	can name which subdirectory to make the output relative
+	to by giving a <path> as an argument.
+
 --text::
 	Treat all files as text.
 

diff --git a/Documentation/git-diff.txt b/Documentation/git-diff.txt
index 012bbdc..57c2862 100644
--- a/Documentation/git-diff.txt
+++ b/Documentation/git-diff.txt

@@ -78,11 +78,6 @@ OPTIONS
 :git-diff: 1
 include::diff-options.txt[]
 
---relative::
-	When run from a subdirectory of the project, it can be
-	told to exclude changes outside the directory and show
-	pathnames relative to it with this option.
-
 <path>...::
 	The <paths> parameters, when given, are used to limit
 	the diff to the named paths (you can give directory

diff --git a/diff.c b/diff.c
index db4bd55..2b89b16 100644
--- a/diff.c
+++ b/diff.c

@@ -2302,6 +2302,10 @@ int diff_opt_parse(struct diff_options *options, const char **av, int ac)
 		options->detect_rename = 0;
 	else if (!strcmp(arg, "--relative"))
 		DIFF_OPT_SET(options, RELATIVE_NAME);
+	else if (!prefixcmp(arg, "--relative=")) {
+		DIFF_OPT_SET(options, RELATIVE_NAME);
+		options->prefix = arg + 11;
+	}
 
 	/* xdiff options */
 	else if (!strcmp(arg, "-w") || !strcmp(arg, "--ignore-all-space"))

diff --git a/revision.c b/revision.c
index 6d9188b..4d6f57b 100644
--- a/revision.c
+++ b/revision.c

@@ -720,7 +720,7 @@ void init_revisions(struct rev_info *revs, const char *prefix)
 	revs->commit_format = CMIT_FMT_DEFAULT;
 
 	diff_setup(&revs->diffopt);
-	if (prefix) {
+	if (prefix && !revs->diffopt.prefix) {
 		revs->diffopt.prefix = prefix;
 		revs->diffopt.prefix_length = strlen(prefix);
 	}