shithub: git9

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ref: 0ee6366d9d661574b73d6a419bf53185ec7b9d8d
parent: 32f41dd6f92251af8bf2c8657b46593505ad530e
author: Ori Bernstein <ori@eigenstate.org>
date: Wed Jan 27 00:57:53 EST 2021 

git/serve: set HEAD on first push

If there are no valid refs, and HEAD is invalid, then
pick the ref with the newest commits as the default
branch.

Several people have been caught out by pushing to
a repo where HEAD named differently from what got
pushed, and this is going to be more of a footgun
when 'master', 'main', and 'front' are all in active
use. This should make us pick a useful default in
those cases, instead of silently failing.


--- a/pack.c
+++ b/pack.c
@@ -990,9 +990,10 @@
 {
 	Object *o;
 
-	o = readidxobject(nil, h, 0);
-	if(o)
-		ref(o);
+	if((o = readidxobject(nil, h, 0)) == nil)
+		return nil;
+	parseobject(o);
+	ref(o);
 	return o;
 }
 
--- a/serve.c
+++ b/serve.c
@@ -364,29 +364,45 @@
 updaterefs(Conn *c, Hash *cur, Hash *upd, char **ref, int nupd)
 {
 	char refpath[512];
-	int i, fd, ret, lockfd;
+	int i, newidx, hadref, fd, ret, lockfd;
+	vlong newtm;
 	Object *o;
 	Hash h;
 
 	ret = -1;
+	hadref = 0;
+	newidx = -1;
+	/*
+	 * Date of Magna Carta.
+	 * Wrong because it  was computed using
+	 * the proleptic gregorian calendar.
+	 */
+	newtm = -23811206400;	
 	if((lockfd = lockrepo()) == -1){
 		werrstr("repo locked\n");
 		return -1;
 	}
 	for(i = 0; i < nupd; i++){
-		if(resolveref(&h, ref[i]) == 0 && !hasheq(&h, &cur[i])){
-			werrstr("old ref changed: %s", ref[i]);
-			goto error;
+		if(resolveref(&h, ref[i]) == 0){
+			hadref = 1;
+			if(!hasheq(&h, &cur[i])){
+				werrstr("old ref changed: %s", ref[i]);
+				goto error;
+			}
 		}
 		if((o = readobject(upd[i])) == nil){
 			werrstr("update to nonexistent hash %H", upd[i]);
 			goto error;
 		}
-		unref(o);
 		if(o->type != GCommit){
 			werrstr("not commit: %H", upd[i]);
 			goto error;
 		}
+		if(o->commit->mtime > newtm){
+			newtm = o->commit->mtime;
+			newidx = i;
+		}
+		unref(o);
 		if(snprint(refpath, sizeof(refpath), ".git/%s", ref[i]) == sizeof(refpath)){
 			werrstr("ref path too long: %s", ref[i]);
 			goto error;
@@ -402,7 +418,30 @@
 		}
 		close(fd);
 	}
-		
+	/*
+	 * Heuristic:
+	 * If there are no valid refs, and HEAD is invalid, then
+	 * pick the ref with the newest commits as the default
+	 * branch.
+	 *
+	 * Several people have been caught out by pushing to
+	 * a repo where HEAD named differently from what got
+	 * pushed, and this is going to be more of a footgun
+	 * when 'master', 'main', and 'front' are all in active
+	 * use. This should make us pick a useful default in
+	 * those cases, instead of silently failing.
+	 */
+	if(resolveref(&h, "HEAD") == -1 && hadref == 0 && newidx != -1){
+		if((fd = create(".git/HEAD", OWRITE|OTRUNC, 0644)) == -1){
+			werrstr("open HEAD: %r");
+			goto error;
+		}
+		if(fprint(fd, "ref: %s", ref[0]) == -1){
+			werrstr("write HEAD ref: %r");
+			goto error;
+		}
+		close(fd);
+	}
 	ret = 0;
 error:
 	fmtpkt(c, "ERR %r");