racy-git: an empty blob has a fixed object name

diff --git a/read-cache.c b/read-cache.c
index 657f0c5894c65831b80ceee54d161d0beac1d733..6fa3c21148979791f18bc0b5c3ed76952acad9ff 100644 (file)
--- a/read-cache.c
+++ b/read-cache.c
@@ -197,6 +197,16 @@ static int ce_modified_check_fs(struct cache_entry *ce, struct stat *st)
        return 0;
 }
 
+static int is_empty_blob_sha1(const unsigned char *sha1)
+{
+       static const unsigned char empty_blob_sha1[20] = {
+               0xe6,0x9d,0xe2,0x9b,0xb2,0xd1,0xd6,0x43,0x4b,0x8b,
+               0x29,0xae,0x77,0x5a,0xd8,0xc2,0xe4,0x8c,0x53,0x91
+       };
+
+       return !hashcmp(sha1, empty_blob_sha1);
+}
+
 static int ce_match_stat_basic(struct cache_entry *ce, struct stat *st)
 {
        unsigned int changed = 0;
@@ -252,16 +262,22 @@ static int ce_match_stat_basic(struct cache_entry *ce, struct stat *st)
        if (ce->ce_size != (unsigned int) st->st_size)
                changed |= DATA_CHANGED;
 
+       /* Racily smudged entry? */
+       if (!ce->ce_size) {
+               if (!is_empty_blob_sha1(ce->sha1))
+                       changed |= DATA_CHANGED;
+       }
+
        return changed;
 }
 
-static int is_racy_timestamp(struct index_state *istate, struct cache_entry *ce)
+static int is_racy_timestamp(const struct index_state *istate, struct cache_entry *ce)
 {
        return (istate->timestamp &&
                ((unsigned int)istate->timestamp) <= ce->ce_mtime);
 }
 
-int ie_match_stat(struct index_state *istate,
+int ie_match_stat(const struct index_state *istate,
                  struct cache_entry *ce, struct stat *st,
                  unsigned int options)
 {
@@ -304,7 +320,7 @@ int ie_match_stat(struct index_state *istate,
        return changed;
 }
 
-int ie_modified(struct index_state *istate,
+int ie_modified(const struct index_state *istate,
                struct cache_entry *ce, struct stat *st, unsigned int options)
 {
        int changed, changed_fs;
@@ -351,6 +367,41 @@ int base_name_compare(const char *name1, int len1, int mode1,
        return (c1 < c2) ? -1 : (c1 > c2) ? 1 : 0;
 }
 
+/*
+ * df_name_compare() is identical to base_name_compare(), except it
+ * compares conflicting directory/file entries as equal. Note that
+ * while a directory name compares as equal to a regular file, they
+ * then individually compare _differently_ to a filename that has
+ * a dot after the basename (because '\0' < '.' < '/').
+ *
+ * This is used by routines that want to traverse the git namespace
+ * but then handle conflicting entries together when possible.
+ */
+int df_name_compare(const char *name1, int len1, int mode1,
+                   const char *name2, int len2, int mode2)
+{
+       int len = len1 < len2 ? len1 : len2, cmp;
+       unsigned char c1, c2;
+
+       cmp = memcmp(name1, name2, len);
+       if (cmp)
+               return cmp;
+       /* Directories and files compare equal (same length, same name) */
+       if (len1 == len2)
+               return 0;
+       c1 = name1[len];
+       if (!c1 && S_ISDIR(mode1))
+               c1 = '/';
+       c2 = name2[len];
+       if (!c2 && S_ISDIR(mode2))
+               c2 = '/';
+       if (c1 == '/' && !c2)
+               return 0;
+       if (c2 == '/' && !c1)
+               return 0;
+       return c1 - c2;
+}
+
 int cache_name_compare(const char *name1, int flags1, const char *name2, int flags2)
 {
        int len1 = flags1 & CE_NAMEMASK;
@@ -377,7 +428,7 @@ int cache_name_compare(const char *name1, int flags1, const char *name2, int fla
        return 0;
 }
 
-int index_name_pos(struct index_state *istate, const char *name, int namelen)
+int index_name_pos(const struct index_state *istate, const char *name, int namelen)
 {
        int first, last;
 
@@ -1166,7 +1217,7 @@ int discard_index(struct index_state *istate)
        return 0;
 }
 
-int unmerged_index(struct index_state *istate)
+int unmerged_index(const struct index_state *istate)
 {
        int i;
        for (i = 0; i < istate->cache_nr; i++) {
@@ -1311,7 +1362,7 @@ static int ce_write_entry(SHA_CTX *c, int fd, struct cache_entry *ce)
        return ce_write(c, fd, ondisk, size);
 }
 
-int write_index(struct index_state *istate, int newfd)
+int write_index(const struct index_state *istate, int newfd)
 {
        SHA_CTX c;
        struct cache_header hdr;