unpack-objects desperately salvages objects from a corrupt pack

The command unpack-objects dies upon the first error.  This is
probably considered a feature -- if a pack is corrupt, instead
of trying to extract from it and possibly risking to contaminate
a good repository with objects whose validity is dubious, we
should seek a good copy of the pack and retry.  However, we may
not have any good copy anywhere.  This implements the last
resort effort to extract what are salvageable from such a
corrupt pack.

This flag might have helped Sergio when recovering from a
corrupt pack.  In my test, it managed to salvage 247 objects out
of a pack that had 251 objects but without it the command
stopped after extracting 73 objects.

Signed-off-by: Junio C Hamano <junkio@cox.net>

diff --git a/Documentation/git-unpack-objects.txt b/Documentation/git-unpack-objects.txt
index c20b38b08adca264316f35b064153213a0bfd7c3..415c09ba10a391cec60c939da1722c83df7cd906 100644 (file)
--- a/Documentation/git-unpack-objects.txt
+++ b/Documentation/git-unpack-objects.txt
@@ -8,7 +8,7 @@ git-unpack-objects - Unpack objects from a packed archive
 
 SYNOPSIS
 --------
-'git-unpack-objects' [-n] [-q] <pack-file
+'git-unpack-objects' [-n] [-q] [-r] <pack-file
 
 
 DESCRIPTION
@@ -34,6 +34,12 @@ OPTIONS
        The command usually shows percentage progress.  This
        flag suppresses it.
 
+-r::
+       When unpacking a corrupt packfile, the command dies at
+       the first corruption.  This flag tells it to keep going
+       and make the best effort to salvage as many objects as
+       possible.
+
 
 Author
 ------

diff --git a/builtin-unpack-objects.c b/builtin-unpack-objects.c
index 0c180b53a32dc316bcbc614caee84eda109c5a59..5f9c0d2f9ec17599fdd9a7203fe334bfdcadb848 100644 (file)
--- a/builtin-unpack-objects.c
+++ b/builtin-unpack-objects.c
@@ -10,7 +10,7 @@
 
 #include <sys/time.h>
 
-static int dry_run, quiet;
+static int dry_run, quiet, desperate, has_errors;
 static const char unpack_usage[] = "git-unpack-objects [-n] [-q] < pack-file";
 
 /* We always read in 4kB chunks. */
@@ -71,8 +71,15 @@ static void *get_data(unsigned long size)
                use(len - stream.avail_in);
                if (stream.total_out == size && ret == Z_STREAM_END)
                        break;
-               if (ret != Z_OK)
-                       die("inflate returned %d\n", ret);
+               if (ret != Z_OK) {
+                       error("inflate returned %d\n", ret);
+                       free(buf);
+                       buf = NULL;
+                       if (!desperate)
+                               exit(1);
+                       has_errors = 1;
+                       break;
+               }
                stream.next_in = fill(1);
                stream.avail_in = len;
        }
@@ -110,9 +117,9 @@ static void write_object(void *buf, unsigned long size, const char *type)
        added_object(sha1, type, buf, size);
 }
 
-static int resolve_delta(const char *type,
-       void *base, unsigned long base_size,
-       void *delta, unsigned long delta_size)
+static void resolve_delta(const char *type,
+                         void *base, unsigned long base_size,
+                         void *delta, unsigned long delta_size)
 {
        void *result;
        unsigned long result_size;
@@ -125,7 +132,6 @@ static int resolve_delta(const char *type,
        free(delta);
        write_object(result, result_size, type);
        free(result);
-       return 0;
 }
 
 static void added_object(unsigned char *sha1, const char *type, void *data, unsigned long size)
@@ -145,7 +151,7 @@ static void added_object(unsigned char *sha1, const char *type, void *data, unsi
        }
 }
 
-static int unpack_non_delta_entry(enum object_type kind, unsigned long size)
+static void unpack_non_delta_entry(enum object_type kind, unsigned long size)
 {
        void *buf = get_data(size);
        const char *type;
@@ -157,39 +163,42 @@ static int unpack_non_delta_entry(enum object_type kind, unsigned long size)
        case OBJ_TAG:    type = tag_type; break;
        default: die("bad type %d", kind);
        }
-       if (!dry_run)
+       if (!dry_run && buf)
                write_object(buf, size, type);
        free(buf);
-       return 0;
 }
 
-static int unpack_delta_entry(unsigned long delta_size)
+static void unpack_delta_entry(unsigned long delta_size)
 {
        void *delta_data, *base;
        unsigned long base_size;
        char type[20];
        unsigned char base_sha1[20];
-       int result;
 
        hashcpy(base_sha1, fill(20));
        use(20);
 
        delta_data = get_data(delta_size);
-       if (dry_run) {
+       if (dry_run || !delta_data) {
                free(delta_data);
-               return 0;
+               return;
        }
 
        if (!has_sha1_file(base_sha1)) {
                add_delta_to_list(base_sha1, delta_data, delta_size);
-               return 0;
+               return;
        }
        base = read_sha1_file(base_sha1, type, &base_size);
-       if (!base)
-               die("failed to read delta-pack base object %s", sha1_to_hex(base_sha1));
-       result = resolve_delta(type, base, base_size, delta_data, delta_size);
+       if (!base) {
+               error("failed to read delta-pack base object %s",
+                     sha1_to_hex(base_sha1));
+               if (!desperate)
+                       exit(1);
+               has_errors = 1;
+               return;
+       }
+       resolve_delta(type, base, base_size, delta_data, delta_size);
        free(base);
-       return result;
 }
 
 static void unpack_one(unsigned nr, unsigned total)
@@ -236,7 +245,11 @@ static void unpack_one(unsigned nr, unsigned total)
                unpack_delta_entry(size);
                return;
        default:
-               die("bad object type %d", type);
+               error("bad object type %d", type);
+               has_errors = 1;
+               if (desperate)
+                       return;
+               exit(1);
        }
 }
 
@@ -280,6 +293,10 @@ int cmd_unpack_objects(int argc, const char **argv, const char *prefix)
                                quiet = 1;
                                continue;
                        }
+                       if (!strcmp(arg, "-r")) {
+                               desperate = 1;
+                               continue;
+                       }
                        usage(unpack_usage);
                }
 
@@ -306,5 +323,5 @@ int cmd_unpack_objects(int argc, const char **argv, const char *prefix)
        /* All done */
        if (!quiet)
                fprintf(stderr, "\n");
-       return 0;
+       return has_errors;
 }