Support 'master@2 hours ago' syntax

Extended sha1 expressions may now include date specifications
which indicate a point in time within the local repository's
history.  If the ref indicated to the left of '@' has a log in
$GIT_DIR/logs/<ref> then the value of the ref at the time indicated
by the specification is obtained from the ref's log.

Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>

diff --git a/Documentation/git-rev-parse.txt b/Documentation/git-rev-parse.txt
index ab896fc..df308c3 100644 (file)
--- a/Documentation/git-rev-parse.txt
+++ b/Documentation/git-rev-parse.txt
@@ -124,6 +124,12 @@ syntax.
   happen to have both heads/master and tags/master, you can
   explicitly say 'heads/master' to tell git which one you mean.
 
+* A suffix '@' followed by a date specification such as 'yesterday'
+  (24 hours ago) or '1 month 2 weeks 3 days 1 hour 1 second ago'
+  to specify the value of the ref at a prior point in time.
+  This suffix may only be used immediately following a ref name
+  and the ref must have an existing log ($GIT_DIR/logs/<ref>).
+
 * A suffix '{caret}' to a revision parameter means the first parent of
   that commit object.  '{caret}<n>' means the <n>th parent (i.e.
   'rev{caret}'

diff --git a/refs.c b/refs.c
index 4be75a5..4c99e37 100644 (file)
--- a/refs.c
+++ b/refs.c
@@ -429,3 +429,56 @@ int write_ref_sha1(struct ref_lock *lock,
        unlock_ref(lock);
        return 0;
 }
+
+int read_ref_at(const char *ref, unsigned long at_time, unsigned char *sha1)
+{
+       const char *logfile, *logdata, *logend, *rec, *c;
+       char *tz_c;
+       int logfd, tz;
+       struct stat st;
+       unsigned long date;
+
+       logfile = git_path("logs/%s", ref);
+       logfd = open(logfile, O_RDONLY, 0);
+       if (logfd < 0)
+               die("Unable to read log %s: %s", logfile, strerror(errno));
+       fstat(logfd, &st);
+       if (!st.st_size)
+               die("Log %s is empty.", logfile);
+       logdata = mmap(NULL, st.st_size, PROT_READ, MAP_PRIVATE, logfd, 0);
+       close(logfd);
+
+       rec = logend = logdata + st.st_size;
+       while (logdata < rec) {
+               if (logdata < rec && *(rec-1) == '\n')
+                       rec--;
+               while (logdata < rec && *(rec-1) != '\n')
+                       rec--;
+               c = rec;
+               while (c < logend && *c != '>' && *c != '\n')
+                       c++;
+               if (c == logend || *c == '\n')
+                       die("Log %s is corrupt.", logfile);
+               date = strtoul(c, NULL, 10);
+               if (date <= at_time) {
+                       if (get_sha1_hex(rec + 41, sha1))
+                               die("Log %s is corrupt.", logfile);
+                       munmap((void*)logdata, st.st_size);
+                       return 0;
+               }
+       }
+
+       c = logdata;
+       while (c < logend && *c != '>' && *c != '\n')
+               c++;
+       if (c == logend || *c == '\n')
+               die("Log %s is corrupt.", logfile);
+       date = strtoul(c, &tz_c, 10);
+       tz = strtoul(tz_c, NULL, 10);
+       if (get_sha1_hex(logdata, sha1))
+               die("Log %s is corrupt.", logfile);
+       munmap((void*)logdata, st.st_size);
+       fprintf(stderr, "warning: Log %s only goes back to %s.\n",
+               logfile, show_rfc2822_date(date, tz));
+       return 0;
+}

diff --git a/refs.h b/refs.h
index 43831e9..2c854de 100644 (file)
--- a/refs.h
+++ b/refs.h
@@ -34,6 +34,9 @@ extern void unlock_ref (struct ref_lock *lock);
 /** Writes sha1 into the ref specified by the lock. **/
 extern int write_ref_sha1(struct ref_lock *lock, const unsigned char *sha1, const char *msg);
 
+/** Reads log for the value of ref during at_time. **/
+extern int read_ref_at(const char *ref, unsigned long at_time, unsigned char *sha1);
+
 /** Returns 0 if target has the right format for a ref. **/
 extern int check_ref_format(const char *target);
 

diff --git a/sha1_name.c b/sha1_name.c
index dc68355..3ac3ab4 100644 (file)
--- a/sha1_name.c
+++ b/sha1_name.c
@@ -4,6 +4,7 @@
 #include "tree.h"
 #include "blob.h"
 #include "tree-walk.h"
+#include "refs.h"
 
 static int find_short_object_filename(int len, const char *name, unsigned char *sha1)
 {
@@ -245,36 +246,60 @@ static int get_sha1_basic(const char *str, int len, unsigned char *sha1)
                "refs/remotes/%.*s/HEAD",
                NULL
        };
-       const char **p;
-       const char *warning = "warning: refname '%.*s' is ambiguous.\n";
-       char *pathname;
-       int already_found = 0;
+       static const char *warning = "warning: refname '%.*s' is ambiguous.\n";
+       const char **p, *pathname;
+       char *real_path = NULL;
+       int refs_found = 0, at_mark;
+       unsigned long at_time = (unsigned long)-1;
        unsigned char *this_result;
        unsigned char sha1_from_ref[20];
 
        if (len == 40 && !get_sha1_hex(str, sha1))
                return 0;
 
+       /* At a given period of time? "@2 hours ago" */
+       for (at_mark = 1; at_mark < len; at_mark++) {
+               if (str[at_mark] == '@') {
+                       int date_len = len - at_mark - 1;
+                       char *date_spec = xmalloc(date_len + 1);
+                       strncpy(date_spec, str + at_mark + 1, date_len);
+                       date_spec[date_len] = 0;
+                       at_time = approxidate(date_spec);
+                       free(date_spec);
+                       len = at_mark;
+               }
+       }
+
        /* Accept only unambiguous ref paths. */
        if (ambiguous_path(str, len))
                return -1;
 
        for (p = fmt; *p; p++) {
-               this_result = already_found ? sha1_from_ref : sha1;
-               pathname = git_path(*p, len, str);
-               if (!read_ref(pathname, this_result)) {
-                       if (warn_ambiguous_refs) {
-                               if (already_found)
-                                       fprintf(stderr, warning, len, str);
-                               already_found++;
-                       }
-                       else
-                               return 0;
+               this_result = refs_found ? sha1_from_ref : sha1;
+               pathname = resolve_ref(git_path(*p, len, str), this_result, 1);
+               if (pathname) {
+                       if (!refs_found++)
+                               real_path = strdup(pathname);
+                       if (!warn_ambiguous_refs)
+                               break;
                }
        }
-       if (already_found)
-               return 0;
-       return -1;
+
+       if (!refs_found)
+               return -1;
+
+       if (warn_ambiguous_refs && refs_found > 1)
+               fprintf(stderr, warning, len, str);
+
+       if (at_time != (unsigned long)-1) {
+               read_ref_at(
+                       real_path + strlen(git_path(".")) - 1,
+                       at_time,
+                       sha1);
+       }
+
+       free(real_path);
+       return 0;
 }
 
 static int get_sha1_1(const char *name, int len, unsigned char *sha1);