drop vcs-svn experiment

The code in vcs-svn was started in 2010 as an attempt to build a
remote-helper for interacting with svn repositories (as opposed to
git-svn). However, we never got as far as shipping a mature remote
helper, and the last substantive commit was e99d012a6bc in 2012.

We do have a git-remote-testsvn, and it is even installed as part of
"make install". But given the name, it seems unlikely to be used by
anybody (you'd have to explicitly "git clone testsvn::$url", and there
have been zero mentions of that on the mailing list since 2013, and even
that includes the phrase "you might need to hack a bit to get it working
properly"[1]).

We also ship contrib/svn-fe, which builds on the vcs-svn work. However,
it does not seem to build out of the box for me, as the link step misses
some required libraries for using libgit.a. Curiously, the original
build breakage bisects for me to eff80a9fd9 (Allow custom "comment
char", 2013-01-16), which seems unrelated. There was an attempt to fix
it in da011cb0e7 (contrib/svn-fe: fix Makefile, 2014-08-28), but on my
system that only switches the error message.

So it seems like the result is not really usable by anybody in practice.
It would be wonderful if somebody wanted to pick up the topic again, and
potentially it's worth carrying around for that reason. But the flip
side is that people doing tree-wide operations have to deal with this
code.  And you can see the list with (replace "HEAD" with this commit as
appropriate):

  {
    echo "--"
    git diff-tree --diff-filter=D -r --name-only HEAD^ HEAD
  } |
  git log --no-merges --oneline e99d012a6bc.. --stdin

which shows 58 times somebody had to deal with the code, generally due
to a compile or test failure, or a tree-wide style fix or API change.
Let's drop it and let anybody who wants to pick it up do so by
resurrecting it from the git history.

As a bonus, this also reduces the size of a stripped installation of Git
from 21MB to 19MB.

[1] https://lore.kernel.org/git/CALkWK0mPHzKfzFKKpZkfAus3YVC9NFYDbFnt+5JQYVKipk3bQQ@mail.gmail.com/

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 0 insertions, 309 deletions

diff --git a/vcs-svn/svndiff.c b/vcs-svn/svndiff.c
deleted file mode 100644
index 75c753162a..0000000000
--- a/vcs-svn/svndiff.c
+++ /dev/null
@@ -1,309 +0,0 @@
-/*
- * Licensed under a two-clause BSD-style license.
- * See LICENSE for details.
- */
-
-#include "git-compat-util.h"
-#include "sliding_window.h"
-#include "line_buffer.h"
-#include "svndiff.h"
-
-/*
- * svndiff0 applier
- *
- * See http://svn.apache.org/repos/asf/subversion/trunk/notes/svndiff.
- *
- * svndiff0 ::= 'SVN\0' window*
- * window ::= int int int int int instructions inline_data;
- * instructions ::= instruction*;
- * instruction ::= view_selector int int
- *   | copyfrom_data int
- *   | packed_view_selector int
- *   | packed_copyfrom_data
- *   ;
- * view_selector ::= copyfrom_source
- *   | copyfrom_target
- *   ;
- * copyfrom_source ::= # binary 00 000000;
- * copyfrom_target ::= # binary 01 000000;
- * copyfrom_data ::= # binary 10 000000;
- * packed_view_selector ::= # view_selector OR-ed with 6 bit value;
- * packed_copyfrom_data ::= # copyfrom_data OR-ed with 6 bit value;
- * int ::= highdigit* lowdigit;
- * highdigit ::= # binary 1000 0000 OR-ed with 7 bit value;
- * lowdigit ::= # 7 bit value;
- */
-
-#define INSN_MASK	0xc0
-#define INSN_COPYFROM_SOURCE	0x00
-#define INSN_COPYFROM_TARGET	0x40
-#define INSN_COPYFROM_DATA	0x80
-#define OPERAND_MASK	0x3f
-
-#define VLI_CONTINUE	0x80
-#define VLI_DIGIT_MASK	0x7f
-#define VLI_BITS_PER_DIGIT 7
-
-struct window {
-	struct sliding_view *in;
-	struct strbuf out;
-	struct strbuf instructions;
-	struct strbuf data;
-};
-
-#define WINDOW_INIT(w)	{ (w), STRBUF_INIT, STRBUF_INIT, STRBUF_INIT }
-
-static void window_release(struct window *ctx)
-{
-	strbuf_release(&ctx->out);
-	strbuf_release(&ctx->instructions);
-	strbuf_release(&ctx->data);
-}
-
-static int write_strbuf(struct strbuf *sb, FILE *out)
-{
-	if (fwrite(sb->buf, 1, sb->len, out) == sb->len)	/* Success. */
-		return 0;
-	return error_errno("cannot write delta postimage");
-}
-
-static int error_short_read(struct line_buffer *input)
-{
-	if (buffer_ferror(input))
-		return error_errno("error reading delta");
-	return error("invalid delta: unexpected end of file");
-}
-
-static int read_chunk(struct line_buffer *delta, off_t *delta_len,
-		      struct strbuf *buf, size_t len)
-{
-	assert(*delta_len >= 0);
-	strbuf_reset(buf);
-	if (len > (uintmax_t) *delta_len ||
-	    buffer_read_binary(delta, buf, len) != len)
-		return error_short_read(delta);
-	*delta_len -= buf->len;
-	return 0;
-}
-
-static int read_magic(struct line_buffer *in, off_t *len)
-{
-	static const char magic[] = {'S', 'V', 'N', '\0'};
-	struct strbuf sb = STRBUF_INIT;
-
-	if (read_chunk(in, len, &sb, sizeof(magic))) {
-		strbuf_release(&sb);
-		return -1;
-	}
-	if (memcmp(sb.buf, magic, sizeof(magic))) {
-		strbuf_release(&sb);
-		return error("invalid delta: unrecognized file type");
-	}
-	strbuf_release(&sb);
-	return 0;
-}
-
-static int read_int(struct line_buffer *in, uintmax_t *result, off_t *len)
-{
-	uintmax_t rv = 0;
-	off_t sz;
-	for (sz = *len; sz; sz--) {
-		const int ch = buffer_read_char(in);
-		if (ch == EOF)
-			break;
-
-		rv <<= VLI_BITS_PER_DIGIT;
-		rv += (ch & VLI_DIGIT_MASK);
-		if (ch & VLI_CONTINUE)
-			continue;
-
-		*result = rv;
-		*len = sz - 1;
-		return 0;
-	}
-	return error_short_read(in);
-}
-
-static int parse_int(const char **buf, size_t *result, const char *end)
-{
-	size_t rv = 0;
-	const char *pos;
-	for (pos = *buf; pos != end; pos++) {
-		unsigned char ch = *pos;
-
-		rv <<= VLI_BITS_PER_DIGIT;
-		rv += (ch & VLI_DIGIT_MASK);
-		if (ch & VLI_CONTINUE)
-			continue;
-
-		*result = rv;
-		*buf = pos + 1;
-		return 0;
-	}
-	return error("invalid delta: unexpected end of instructions section");
-}
-
-static int read_offset(struct line_buffer *in, off_t *result, off_t *len)
-{
-	uintmax_t val;
-	if (read_int(in, &val, len))
-		return -1;
-	if (val > maximum_signed_value_of_type(off_t))
-		return error("unrepresentable offset in delta: %"PRIuMAX"", val);
-	*result = val;
-	return 0;
-}
-
-static int read_length(struct line_buffer *in, size_t *result, off_t *len)
-{
-	uintmax_t val;
-	if (read_int(in, &val, len))
-		return -1;
-	if (val > SIZE_MAX)
-		return error("unrepresentable length in delta: %"PRIuMAX"", val);
-	*result = val;
-	return 0;
-}
-
-static int copyfrom_source(struct window *ctx, const char **instructions,
-			   size_t nbytes, const char *insns_end)
-{
-	size_t offset;
-	if (parse_int(instructions, &offset, insns_end))
-		return -1;
-	if (unsigned_add_overflows(offset, nbytes) ||
-	    offset + nbytes > ctx->in->width)
-		return error("invalid delta: copies source data outside view");
-	strbuf_add(&ctx->out, ctx->in->buf.buf + offset, nbytes);
-	return 0;
-}
-
-static int copyfrom_target(struct window *ctx, const char **instructions,
-			   size_t nbytes, const char *instructions_end)
-{
-	size_t offset;
-	if (parse_int(instructions, &offset, instructions_end))
-		return -1;
-	if (offset >= ctx->out.len)
-		return error("invalid delta: copies from the future");
-	for (; nbytes > 0; nbytes--)
-		strbuf_addch(&ctx->out, ctx->out.buf[offset++]);
-	return 0;
-}
-
-static int copyfrom_data(struct window *ctx, size_t *data_pos, size_t nbytes)
-{
-	const size_t pos = *data_pos;
-	if (unsigned_add_overflows(pos, nbytes) ||
-	    pos + nbytes > ctx->data.len)
-		return error("invalid delta: copies unavailable inline data");
-	strbuf_add(&ctx->out, ctx->data.buf + pos, nbytes);
-	*data_pos += nbytes;
-	return 0;
-}
-
-static int parse_first_operand(const char **buf, size_t *out, const char *end)
-{
-	size_t result = (unsigned char) *(*buf)++ & OPERAND_MASK;
-	if (result) {	/* immediate operand */
-		*out = result;
-		return 0;
-	}
-	return parse_int(buf, out, end);
-}
-
-static int execute_one_instruction(struct window *ctx,
-				const char **instructions, size_t *data_pos)
-{
-	unsigned int instruction;
-	const char *insns_end = ctx->instructions.buf + ctx->instructions.len;
-	size_t nbytes;
-	assert(ctx);
-	assert(instructions && *instructions);
-	assert(data_pos);
-
-	instruction = (unsigned char) **instructions;
-	if (parse_first_operand(instructions, &nbytes, insns_end))
-		return -1;
-	switch (instruction & INSN_MASK) {
-	case INSN_COPYFROM_SOURCE:
-		return copyfrom_source(ctx, instructions, nbytes, insns_end);
-	case INSN_COPYFROM_TARGET:
-		return copyfrom_target(ctx, instructions, nbytes, insns_end);
-	case INSN_COPYFROM_DATA:
-		return copyfrom_data(ctx, data_pos, nbytes);
-	default:
-		return error("invalid delta: unrecognized instruction");
-	}
-}
-
-static int apply_window_in_core(struct window *ctx)
-{
-	const char *instructions;
-	size_t data_pos = 0;
-
-	/*
-	 * Fill ctx->out.buf using data from the source, target,
-	 * and inline data views.
-	 */
-	for (instructions = ctx->instructions.buf;
-	     instructions != ctx->instructions.buf + ctx->instructions.len;
-	     )
-		if (execute_one_instruction(ctx, &instructions, &data_pos))
-			return -1;
-	if (data_pos != ctx->data.len)
-		return error("invalid delta: does not copy all inline data");
-	return 0;
-}
-
-static int apply_one_window(struct line_buffer *delta, off_t *delta_len,
-			    struct sliding_view *preimage, FILE *out)
-{
-	int rv = -1;
-	struct window ctx = WINDOW_INIT(preimage);
-	size_t out_len;
-	size_t instructions_len;
-	size_t data_len;
-	assert(delta_len);
-
-	/* "source view" offset and length already handled; */
-	if (read_length(delta, &out_len, delta_len) ||
-	    read_length(delta, &instructions_len, delta_len) ||
-	    read_length(delta, &data_len, delta_len) ||
-	    read_chunk(delta, delta_len, &ctx.instructions, instructions_len) ||
-	    read_chunk(delta, delta_len, &ctx.data, data_len))
-		goto error_out;
-	strbuf_grow(&ctx.out, out_len);
-	if (apply_window_in_core(&ctx))
-		goto error_out;
-	if (ctx.out.len != out_len) {
-		rv = error("invalid delta: incorrect postimage length");
-		goto error_out;
-	}
-	if (write_strbuf(&ctx.out, out))
-		goto error_out;
-	rv = 0;
-error_out:
-	window_release(&ctx);
-	return rv;
-}
-
-int svndiff0_apply(struct line_buffer *delta, off_t delta_len,
-			struct sliding_view *preimage, FILE *postimage)
-{
-	assert(delta && preimage && postimage && delta_len >= 0);
-
-	if (read_magic(delta, &delta_len))
-		return -1;
-	while (delta_len) {	/* For each window: */
-		off_t pre_off = -1;
-		size_t pre_len;
-
-		if (read_offset(delta, &pre_off, &delta_len) ||
-		    read_length(delta, &pre_len, &delta_len) ||
-		    move_window(preimage, pre_off, pre_len) ||
-		    apply_one_window(delta, &delta_len, preimage, postimage))
-			return -1;
-	}
-	return 0;
-}