Re: Tabs in commit messages - de-tabify option in strbuf_stripspace()?

[Linus Torvalds <torvalds@linux-foundation.org>]

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On Tue, Mar 15, 2016 at 5:48 PM, Linus Torvalds
<torvalds@linux-foundation.org> wrote:
> On Tue, Mar 15, 2016 at 5:45 PM, Junio C Hamano <gitster@pobox.com> wrote:
>>
>> Wouldn't it be nicer to do this kind of thing at the output side?  A
>> stupid way would be to have an option to indent the log text with a
>> tab instead of 4-spaces, but a more sensible way would be to keep
>> the visual 4-space-indent and do the expand-tab for each line of
>> text.
>
> Yes, that would certainly work for me too. It's just the "ascii boxes
> don't line up" that is problematic..

Ok, that actually turns out to be pretty easy.

Here's a first try at it. It does tab expansion only for the cases
that indent the commit message, so for things like "pretty=email" it
makes no difference at all.

However, it hardcodes the hardtab size to 8, and makes this all
unconditional. That's how a vt100 terminal works, but fancer terminals
may allow you set actual tab-stops, and if you're in emacs you can
probably do just about anything)

Comments? This does make the kernel commit 0dc8c730c98a look fine, so
it would make me happy.

I can write a commit log etc if people think this is ok, but right now
this is just a silly raw patch in the attachement..

               Linus

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 pretty.c | 20 +++++++++++++++++++-
 1 file changed, 19 insertions(+), 1 deletion(-)

diff --git a/pretty.c b/pretty.c
index 92b2870a7eab..dcd6105d1eb2 100644
--- a/pretty.c
+++ b/pretty.c
@@ -1652,8 +1652,26 @@ void pp_remainder(struct pretty_print_context *pp,
 		first = 0;
 
 		strbuf_grow(sb, linelen + indent + 20);
-		if (indent)
+		if (indent) {
+			int i, last = 0, pos = 0;
+
 			strbuf_addchars(sb, ' ', indent);
+			for (i = 0; i < linelen; i++) {
+				int expand;
+				if (line[i] != '\t')
+					continue;
+				strbuf_add(sb, line+last, i-last);
+				pos += i-last;
+				expand = (pos + 8) & ~7;
+				strbuf_addchars(sb, ' ', expand - pos);
+				pos = expand;
+				last = i+1;
+			}
+
+			// Handle the tail non-tab content
+			line += last;
+			linelen -= last;
+		}
 		strbuf_add(sb, line, linelen);
 		strbuf_addch(sb, '\n');
 	}