odb: refactor parsing of alternates to be self-contained

Parsing of the alternates file and environment variable is currently
split up across multiple different functions and is entangled with
`link_alt_odb_entries()`, which is responsible for linking the parsed
object database sources. This results in two downsides:

  - We have mutual recursion between parsing alternates and linking them
    into the object database. This is because we also parse alternates
    that the newly added sources may have.

  - We mix up the actual logic to parse the data and to link them into
    place.

Refactor the logic so that parsing of the alternates file is entirely
self-contained. Note that this doesn't yet fix the above two issues, but
it is a necessary step to get there.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/odb.c b/odb.c
index dc8f292f3d9645e2de8d990630a29cb4b4b1e20a..9785f62cb6be5e183a9c891f231e8d5f9e73eb5b 100644 (file)
--- a/odb.c
+++ b/odb.c
@@ -216,39 +216,50 @@ static struct odb_source *link_alt_odb_entry(struct object_database *odb,
        return alternate;
 }
 
-static const char *parse_alt_odb_entry(const char *string,
-                                      int sep,
-                                      struct strbuf *out)
+static void parse_alternates(const char *string,
+                            int sep,
+                            struct strvec *out)
 {
-       const char *end;
+       struct strbuf buf = STRBUF_INIT;
 
-       strbuf_reset(out);
+       while (*string) {
+               const char *end;
+
+               strbuf_reset(&buf);
+
+               if (*string == '#') {
+                       /* comment; consume up to next separator */
+                       end = strchrnul(string, sep);
+               } else if (*string == '"' && !unquote_c_style(&buf, string, &end)) {
+                       /*
+                        * quoted path; unquote_c_style has copied the
+                        * data for us and set "end". Broken quoting (e.g.,
+                        * an entry that doesn't end with a quote) falls
+                        * back to the unquoted case below.
+                        */
+               } else {
+                       /* normal, unquoted path */
+                       end = strchrnul(string, sep);
+                       strbuf_add(&buf, string, end - string);
+               }
 
-       if (*string == '#') {
-               /* comment; consume up to next separator */
-               end = strchrnul(string, sep);
-       } else if (*string == '"' && !unquote_c_style(out, string, &end)) {
-               /*
-                * quoted path; unquote_c_style has copied the
-                * data for us and set "end". Broken quoting (e.g.,
-                * an entry that doesn't end with a quote) falls
-                * back to the unquoted case below.
-                */
-       } else {
-               /* normal, unquoted path */
-               end = strchrnul(string, sep);
-               strbuf_add(out, string, end - string);
+               if (*end)
+                       end++;
+               string = end;
+
+               if (!buf.len)
+                       continue;
+
+               strvec_push(out, buf.buf);
        }
 
-       if (*end)
-               end++;
-       return end;
+       strbuf_release(&buf);
 }
 
 static void link_alt_odb_entries(struct object_database *odb, const char *alt,
                                 int sep, const char *relative_base, int depth)
 {
-       struct strbuf dir = STRBUF_INIT;
+       struct strvec alternates = STRVEC_INIT;
 
        if (!alt || !*alt)
                return;
@@ -259,13 +270,12 @@ static void link_alt_odb_entries(struct object_database *odb, const char *alt,
                return;
        }
 
-       while (*alt) {
-               alt = parse_alt_odb_entry(alt, sep, &dir);
-               if (!dir.len)
-                       continue;
-               link_alt_odb_entry(odb, dir.buf, relative_base, depth);
-       }
-       strbuf_release(&dir);
+       parse_alternates(alt, sep, &alternates);
+
+       for (size_t i = 0; i < alternates.nr; i++)
+               link_alt_odb_entry(odb, alternates.v[i], relative_base, depth);
+
+       strvec_clear(&alternates);
 }
 
 static void read_info_alternates(struct object_database *odb,