split-index: strip pathname of on-disk replaced entries

We know the positions of replaced entries via the replace bitmap in
"link" extension, so the "name" path does not have to be stored (it's
still in the shared index). With this, we also have a way to
distinguish additions vs replacements at load time and can catch
broken "link" extensions.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/cache.h b/cache.h
index 70fd8ed46219b1730971a89242b128be52828690..ddb7cd26d1d787b06f366db5b0c6621d1cee5268 100644 (file)
--- a/cache.h
+++ b/cache.h
@@ -170,6 +170,7 @@ struct cache_entry {
 #define CE_MATCHED           (1 << 26)
 
 #define CE_UPDATE_IN_BASE    (1 << 27)
+#define CE_STRIP_NAME        (1 << 28)
 
 /*
  * Extended on-disk flags

diff --git a/read-cache.c b/read-cache.c
index d5f70a08b9d475eaf80f9df3aeba524b8fde6cbe..af475dc58cce5acce258be6d8ee3835af88a15b3 100644 (file)
--- a/read-cache.c
+++ b/read-cache.c
@@ -1787,9 +1787,15 @@ static int ce_write_entry(git_SHA_CTX *c, int fd, struct cache_entry *ce,
 {
        int size;
        struct ondisk_cache_entry *ondisk;
+       int saved_namelen = saved_namelen; /* compiler workaround */
        char *name;
        int result;
 
+       if (ce->ce_flags & CE_STRIP_NAME) {
+               saved_namelen = ce_namelen(ce);
+               ce->ce_namelen = 0;
+       }
+
        if (!previous_name) {
                size = ondisk_ce_size(ce);
                ondisk = xcalloc(1, size);
@@ -1821,6 +1827,10 @@ static int ce_write_entry(git_SHA_CTX *c, int fd, struct cache_entry *ce,
                strbuf_splice(previous_name, common, to_remove,
                              ce->name + common, ce_namelen(ce) - common);
        }
+       if (ce->ce_flags & CE_STRIP_NAME) {
+               ce->ce_namelen = saved_namelen;
+               ce->ce_flags &= ~CE_STRIP_NAME;
+       }
 
        result = ce_write(c, fd, ondisk, size);
        free(ondisk);

diff --git a/split-index.c b/split-index.c
index 33c0c4b6983f29bf29a4bcca9706180bd32b59ff..ee3246f391a6ea7524e1bc40b535f33fa662bd3c 100644 (file)
--- a/split-index.c
+++ b/split-index.c
@@ -89,6 +89,7 @@ static void replace_entry(size_t pos, void *data)
        struct index_state *istate = data;
        struct split_index *si = istate->split_index;
        struct cache_entry *dst, *src;
+
        if (pos >= istate->cache_nr)
                die("position for replacement %d exceeds base index size %d",
                    (int)pos, istate->cache_nr);
@@ -100,10 +101,14 @@ static void replace_entry(size_t pos, void *data)
                die("entry %d is marked as both replaced and deleted",
                    (int)pos);
        src = si->saved_cache[si->nr_replacements];
+       if (ce_namelen(src))
+               die("corrupt link extension, entry %d should have "
+                   "zero length name", (int)pos);
        src->index = pos + 1;
        src->ce_flags |= CE_UPDATE_IN_BASE;
-       free(dst);
-       dst = src;
+       src->ce_namelen = dst->ce_namelen;
+       copy_cache_entry(dst, src);
+       free(src);
        si->nr_replacements++;
 }
 
@@ -131,6 +136,9 @@ void merge_base_index(struct index_state *istate)
                remove_marked_cache_entries(istate);
 
        for (i = si->nr_replacements; i < si->saved_cache_nr; i++) {
+               if (!ce_namelen(si->saved_cache[i]))
+                       die("corrupt link extension, entry %d should "
+                           "have non-zero length name", i);
                add_index_entry(istate, si->saved_cache[i],
                                ADD_CACHE_OK_TO_ADD |
                                ADD_CACHE_KEEP_CACHE_TREE |
@@ -213,6 +221,7 @@ void prepare_to_write_split_index(struct index_state *istate)
                                ewah_set(si->delete_bitmap, i);
                        else if (ce->ce_flags & CE_UPDATE_IN_BASE) {
                                ewah_set(si->replace_bitmap, i);
+                               ce->ce_flags |= CE_STRIP_NAME;
                                ALLOC_GROW(entries, nr_entries+1, nr_alloc);
                                entries[nr_entries++] = ce;
                        }
@@ -222,6 +231,7 @@ void prepare_to_write_split_index(struct index_state *istate)
        for (i = 0; i < istate->cache_nr; i++) {
                ce = istate->cache[i];
                if ((!si->base || !ce->index) && !(ce->ce_flags & CE_REMOVE)) {
+                       assert(!(ce->ce_flags & CE_STRIP_NAME));
                        ALLOC_GROW(entries, nr_entries+1, nr_alloc);
                        entries[nr_entries++] = ce;
                }