First part of the format-upgrade support in repo

 In order to work across major bumps, we need to add a call to
s6-rc-format-upgrade before s6-rc-update in the s6-rc-set-install
sequence of commands.
 s6-rc-format-upgrade only works when the db is exactly the same
across s6-rc versions. That means we need to have the source version
of the current live set at all times, in order to compile it with
the new s6-rc version before upgrading and then updating.
 So:
 1. we take a snapshot of the source version of a set every time
we commit.
 2. we refuse to install if we don't have the snapshot.
 3. we add s6-rc-format-upgrade to the processing chain
 4. for cleanup: after installing, we delete all the snapshots of
the set except the one that corresponds to the newly
installed live set.

 This commit implements 1: taking the snapshot. It's a regular
s6-rc-set-copy, using an internal name. We refactor
s6-rc-set-copy and s6-rc-set-delete to have primitives we can
use internally.

 Wait for later commits before using repo, else you'll fill
your repository with snapshots that won't get cleaned up.

 TBD: how to store the s6-rc version in the compiled db. We
probably need to add a small file in there.

1 files changed, 9 insertions, 58 deletions

diff --git a/src/repo/s6-rc-set-copy.c b/src/repo/s6-rc-set-copy.c
index 8cef993..13e14a5 100644
--- a/src/repo/s6-rc-set-copy.c
+++ b/src/repo/s6-rc-set-copy.c
@@ -2,14 +2,10 @@
 
 #include <string.h>
 #include <unistd.h>
-#include <errno.h>
 
 #include <skalibs/uint64.h>
-#include <skalibs/posixplz.h>
 #include <skalibs/envexec.h>
-#include <skalibs/tai.h>
 #include <skalibs/djbunix.h>
-#include <skalibs/unix-transactional.h>
 
 #include <s6-rc/config.h>
 #include <s6-rc/s6rc.h>
@@ -40,68 +36,23 @@ static gol_arg const rgola[] =
   { .so = 'r', .lo = "repodir", .i = GOLA_REPODIR }
 } ;
 
-
-static uint64_t wgolb = 0 ;
-
-static void cleanup (char const *fn)
-{
-  int e = errno ;
-  rm_rf(fn) ;
-  errno = e ;
-}
-
-static inline void docopy (char const *repo, char const *srcname, char const *dstname)
+static inline void docopy (char const *repo, char const *srcname, char const *dstname, uint64_t flags)
 {
-  size_t repolen = strlen(repo) ;
-  size_t srclen = strlen(srcname) ;
-  size_t dstlen = strlen(dstname) ;
-  size_t r ;
-  char src[repolen + srclen + 10] ;
-  char dst[repolen + dstlen + 10] ;
-  char realsrc[repolen + srclen + 18] ;
-  char realdst[repolen + dstlen + 18] ;
-  char olddst[repolen + dstlen + 18] ;
-  memcpy(src, repo, repolen) ;
-  memcpy(src + repolen, "/sources/", 9) ;
-  memcpy(src + repolen + 9, srcname, srclen + 1) ;
-  memcpy(dst, src, repolen + 9) ;
-  memcpy(dst + repolen + 9, dstname, dstlen + 1) ;
-  memcpy(olddst, dst, repolen + 9) ;
-  olddst[repolen + 9] = 0 ;
-  if (access(dst, F_OK) == -1)
-  {
-    if (errno != ENOENT) strerr_diefu2sys(111, "access ", dst) ;
-  }
-  else if (!(wgolb & GOLB_FORCE))
-    strerr_dief4x(1, "set ", dstname, " already exists in repository ", repo) ;
-
-  memcpy(realsrc, src, repolen + 9) ;
-  r = readlink(src, realsrc + repolen + 9, srclen + 9) ;
-  if (r == -1) strerr_diefu2sys(111, "readlink ", src) ;
-  if (r != srclen + 8) strerr_dief3x(102, "symlink ", src, "doesn't point to a valid name") ;
-  realsrc[repolen + srclen + 17] = 0 ;
-  memcpy(realdst, dst, repolen + 9) ;
-  realdst[repolen + 9] = '.' ;
-  memcpy(realdst + repolen + 10, dstname, dstlen) ;
-  memcpy(realdst + repolen + 10 + dstlen, ":XXXXXX", 8) ;
-  if (mkntemp(realdst) == -1) strerr_diefu2sys(111, "mkntemp ", realdst) ;
-  if (!hiercopy(realsrc, realdst))
-  {
-    cleanup(realdst) ;
-    strerr_diefu4sys(111, "copy ", realsrc, " to ", realdst) ;
-  }
-  if (!atomic_symlink4(realdst + repolen + 9, dst, olddst + repolen + 9, dstlen + 9))
+  int e = s6rc_repo_setcopy(repo, srcname, dstname, !!(flags & GOLB_FORCE)) ;
+  switch (e)
   {
-    cleanup(realdst) ;
-    strerr_diefu4sys(111, "symlink ", realdst + repolen + 9, " to ", dst) ;
+    case -2 : strerr_dief(102, "internal layout error: symlink inside ", srcname, " doesn't point to a valid name") ;
+    case -1 : strerr_dief(1, "set ", dstname, " already exists in repository ", repo) ;
+    case 0 : break ;
+    default : strerr_diefusys(111, "copy set ", srcname, " to set ", dstname) ;
   }
-  if (olddst[repolen + 9]) cleanup(olddst) ;
 }
 
 int main (int argc, char const *const *argv)
 {
   int fdlock ;
   unsigned int verbosity = 1 ;
+  uint64_t wgolb = 0 ;
   char const *wgola[GOLA_N] = { 0 } ;
   unsigned int golc ;
 
@@ -121,6 +72,6 @@ int main (int argc, char const *const *argv)
   tain_now_g() ;
   fdlock = s6rc_repo_lock(wgola[GOLA_REPODIR], 1) ;
   if (fdlock == -1) strerr_diefu2sys(111, "lock ", wgola[GOLA_REPODIR]) ;
-  docopy(wgola[GOLA_REPODIR], argv[0], argv[1]) ;
+  docopy(wgola[GOLA_REPODIR], argv[0], argv[1], wgolb) ;
   _exit(0) ;
 }