[PATCH v15 03/16] quote.c: substitute path_relative with relative_path

[Jiang Xin <worldhello.net@gmail.com>]

Substitute the function path_relative in quote.c with the function
relative_path. Function relative_path can be treated as an enhanced
and robust version of path_relative.

Outputs of path_relative and it's replacement (relative_path) are the
same for the following cases:

    path      prefix     output of path_relative  output of relative_path
    ========  =========  =======================  =======================
    /a/b/c/   /a/b/      c/                       c/
    /a/b/c    /a/b/      c                        c
    /a/       /a/b/      ../                      ../
    /         /a/b/      ../../                   ../../
    /a/c      /a/b/      ../c                     ../c
    /x/y      /a/b/      ../../x/y                ../../x/y
    a/b/c/    a/b/       c/                       c/
    a/        a/b/       ../                      ../
    x/y       a/b/      ../../x/y                 ../../x/y
    /a/b      (empty)    /a/b                     /a/b
    /a/b      (null)     /a/b                     /a/b
    a/b       (empty)    a/b                      a/b
    a/b       (null)     a/b                      a/b

But if both of the path and the prefix are the same, or the returned
relative path should be the current directory, the outputs of both
functions are different. Function relative_path returns "./", while
function path_relative returns empty string.

    path      prefix     output of path_relative  output of relative_path
    ========  =========  =======================  =======================
    /a/b/     /a/b/      (empty)                  ./
    a/b/      a/b/       (empty)                  ./
    (empty)   (null)     (empty)                  ./
    (empty)   (empty)    (empty)                  ./

But not panic, the callers of path_relative can handle such cases, or
never encounter this issue at all. E.g.

 * In function quote_path_relative, if the output of path_relative is
   empty, append "./" to it, like:

       if (!out->len)
           strbuf_addstr(out, "./");

 * Another caller is write_name_quoted_relative, which is only used by
   builtin/ls-files.c. git-ls-files only show files, so path of files
   will never be identical with the prefix of a directory.

The following differences show that path_relative can not handle
extra slashes properly.

    path      prefix     output of path_relative  output of relative_path
    ========  =========  =======================  =======================
    /a//b//c/ //a/b//    ../../../../a//b//c/     c/
    a/b//c    a//b       ../b//c                  c

And if prefix has no trailing slash, path_relative can not work properly
either. But since prefix always has a trailing slash, so it's not a
problem.

    path      prefix     output of path_relative  output of relative_path
    ========  =========  =======================  =======================
    /a/b/c/   /a/b       b/c/                     c/
    /a/b      /a/b       b                        ./
    /a/b/     /a/b       b/                       ./
    /a        /a/b/      ../../a                  ../
    a/b/c/    a/b        b/c/                     c/
    a/b/      a/b        b/                       ./
    a         a/b        ../a                     ../
    x/y       a/b/       ../x/y                   ../../x/y
    a/c       a/b        c                        ../c
    /a/       /a/b       (empty)                  ../
    (empty)   /a/b       ../../                   ./

Signed-off-by: Jiang Xin <worldhello.net@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Jiang Xin <worldhello.net@gmail.com>
---
 builtin/ls-files.c |  7 +++++--
 quote.c            | 55 ++----------------------------------------------------
 2 files changed, 7 insertions(+), 55 deletions(-)

diff --git a/builtin/ls-files.c b/builtin/ls-files.c
index 3a410c..d100 100644
--- a/builtin/ls-files.c
+++ b/builtin/ls-files.c
@@ -48,8 +48,11 @@ static const char *tag_resolve_undo = "";
 
 static void write_name(const char* name, size_t len)
 {
-	write_name_quoted_relative(name, len, prefix, prefix_len, stdout,
-			line_terminator);
+	/* Since prefix_len is ignored in write_name_quoted_relative, we
+	 * should turn off prefix here in case of running "git ls-files"
+	 * with "--full-name" option */
+	write_name_quoted_relative(name, len, prefix_len ? prefix : NULL,
+			prefix_len, stdout, line_terminator);
 }
 
 static void show_dir_entry(const char *tag, struct dir_entry *ent)
diff --git a/quote.c b/quote.c
index 91122..64ff3 100644
--- a/quote.c
+++ b/quote.c
@@ -312,75 +312,24 @@ void write_name_quotedpfx(const char *pfx, size_t pfxlen,
 	fputc(terminator, fp);
 }
 
-static const char *path_relative(const char *in, int len,
-				 struct strbuf *sb, const char *prefix,
-				 int prefix_len);
-
 void write_name_quoted_relative(const char *name, size_t len,
 				const char *prefix, size_t prefix_len,
 				FILE *fp, int terminator)
 {
 	struct strbuf sb = STRBUF_INIT;
 
-	name = path_relative(name, len, &sb, prefix, prefix_len);
+	name = relative_path(name, prefix, &sb);
 	write_name_quoted(name, fp, terminator);
 
 	strbuf_release(&sb);
 }
 
-/*
- * Give path as relative to prefix.
- *
- * The strbuf may or may not be used, so do not assume it contains the
- * returned path.
- */
-static const char *path_relative(const char *in, int len,
-				 struct strbuf *sb, const char *prefix,
-				 int prefix_len)
-{
-	int off, i;
-
-	if (len < 0)
-		len = strlen(in);
-	if (prefix_len < 0) {
-		if (prefix)
-			prefix_len = strlen(prefix);
-		else
-			prefix_len = 0;
-	}
-
-	off = 0;
-	i = 0;
-	while (i < prefix_len && i < len && prefix[i] == in[i]) {
-		if (prefix[i] == '/')
-			off = i + 1;
-		i++;
-	}
-	in += off;
-	len -= off;
-
-	if (i >= prefix_len)
-		return in;
-
-	strbuf_reset(sb);
-	strbuf_grow(sb, len);
-
-	while (i < prefix_len) {
-		if (prefix[i] == '/')
-			strbuf_addstr(sb, "../");
-		i++;
-	}
-	strbuf_add(sb, in, len);
-
-	return sb->buf;
-}
-
 /* quote path as relative to the given prefix */
 char *quote_path_relative(const char *in, int len,
 			  struct strbuf *out, const char *prefix)
 {
 	struct strbuf sb = STRBUF_INIT;
-	const char *rel = path_relative(in, len, &sb, prefix, -1);
+	const char *rel = relative_path(in, prefix, &sb);
 	strbuf_reset(out);
 	quote_c_style_counted(rel, strlen(rel), out, NULL, 0);
 	strbuf_release(&sb);
-- 
1.8.3.1.756.g2e9b71f