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.

6 files changed, 137 insertions, 83 deletions

diff --git a/src/repo/deps-lib/s6rcrepo b/src/repo/deps-lib/s6rcrepo
index 7d8b816..1935001 100644
--- a/src/repo/deps-lib/s6rcrepo
+++ b/src/repo/deps-lib/s6rcrepo
@@ -26,6 +26,8 @@ s6rc_repo_rxnames.o
 s6rc_repo_sanitize_setname.o
 s6rc_repo_sanitize_svname.o
 s6rc_repo_setcompile.o
+s6rc_repo_setcopy.o
+s6rc_repo_setdelete.o
 s6rc_repo_setuptodate.o
 s6rc_repo_sv_bcmpr.o
 s6rc_repo_sv_cmpr.o
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) ;
 }
diff --git a/src/repo/s6-rc-set-delete.c b/src/repo/s6-rc-set-delete.c
index 2987033..b32b253 100644
--- a/src/repo/s6-rc-set-delete.c
+++ b/src/repo/s6-rc-set-delete.c
@@ -18,38 +18,18 @@
 #define USAGE "s6-rc-set-delete [ -v verbosity ] [ -r repo ] setname..."
 #define dieusage() strerr_dieusage(100, USAGE)
 
-static inline void dodelete (char const *repo, char const *set)
+static void dodelete_compiled (char const *repo, char const *set)
 {
   size_t repolen = strlen(repo) ;
   size_t setlen = strlen(set) ;
   char fn[repolen + setlen + 11] ;
   memcpy(fn, repo, repolen) ;
-  memcpy(fn + repolen, "/sources/", 9) ;
-  memcpy(fn + repolen + 9, set, setlen + 1) ;
-  if (access(fn, W_OK) == -1)
-  {
-    if (errno != ENOENT) strerr_diefu2sys(111, "access ", fn) ;
-  }
-  else
-  {
-    ssize_t r ;
-    char real[repolen + setlen + 18] ;
-    memcpy(real, repo, repolen) ;
-    memcpy(real + repolen, "/sources/", 9) ;
-    r = readlink(fn, real + repolen + 9, setlen + 9) ;
-    if (r == -1) strerr_diefu2sys(111, "readlink ", fn) ;
-    else if (r != setlen + 8) strerr_dief3x(102, "symlink ", fn, " points to an invalid name") ;
-    real[repolen + setlen + 17] = 0 ;
-    unlink_void(fn) ;
-    rm_rf(real) ;
-  }
-
-  memcpy(fn + repolen + 1, "compiled/", 9) ;
+  memcpy(fn + repolen, "/compiled/", 10) ;
   memcpy(fn + repolen + 10, set, setlen + 1) ;
   unlink_void(fn) ;
   fn[repolen + 9] = 0 ;
   DIR *dir = opendir(fn) ;
-  if (!dir) strerr_diefu2sys(111, "opendir ", fn) ;
+  if (!dir) return ;
   for (;;)
   {
     direntry *d ;
@@ -66,7 +46,6 @@ static inline void dodelete (char const *repo, char const *set)
       rm_rf(tmp) ;
     }
   }
-  if (errno) strerr_diefu2sys(111, "readdir ", fn) ;
   dir_close(dir) ;
 }
 
@@ -105,6 +84,9 @@ int main (int argc, char const *const *argv)
   if (fdlock == -1) strerr_diefu2sys(111, "lock ", wgola[GOLA_REPODIR]) ;
 
   for (unsigned int i = 0 ; i < argc ; i++)
-    dodelete(wgola[GOLA_REPODIR], argv[i]) ;
+  {
+    s6rc_repo_setdelete(wgola[GOLA_REPODIR], argv[i]) ;
+    dodelete_compiled(wgola[GOLA_REPODIR], argv[i]) ;
+  }
   _exit(0) ;
 }
diff --git a/src/repo/s6rc_repo_compile.c b/src/repo/s6rc_repo_compile.c
index 64f8879..83fa744 100644
--- a/src/repo/s6rc_repo_compile.c
+++ b/src/repo/s6rc_repo_compile.c
@@ -22,6 +22,7 @@ int s6rc_repo_compile (char const *repo, char const *set, char const *const *rxs
   size_t setlen = strlen(set) ;
   size_t totrxlen = 0 ;
   int needprefix = strcmp(set, ".ref") ;
+  char snap[repolen + setlen + 37] ;
   char newc[repolen + setlen + 45] ;
   memcpy(newc, repo, repolen) ;
   memcpy(newc + repolen, "/compiled/.", 11) ;
@@ -89,6 +90,26 @@ int s6rc_repo_compile (char const *repo, char const *set, char const *const *rxs
       return (WEXITSTATUS(wstat) == 1) - 1 ;
     }
   }
+
+  if (needprefix)
+  {
+    int e ;
+    memcpy(snap, ".snapshot:", 10) ;
+    memcpy(snap + 10, newc + repolen + 11, setlen + 26) ;
+    snap[repolen + setlen + 36] = 0 ;
+    e = s6rc_repo_setcopy(repo, set, snap, 1) ;
+    switch (e)
+    {
+      case -2 :
+        strerr_warnf("internal layout error while taking a snapshot of set ", set) ;
+        return (errno = EILSEQ, -1) ;
+      case 0 : break ;
+      default :
+        strerr_warnfusys("take a snapshot of set ", set) ;
+        return (errno = e, -1) ;
+    }
+  }
+
   {
     char fn[repolen + setlen + 11] ;
     memcpy(fn, newc, repolen + 10) ;
@@ -97,10 +118,12 @@ int s6rc_repo_compile (char const *repo, char const *set, char const *const *rxs
     {
       int e = errno ;
       rm_rf(newc) ;
+      s6rc_repo_setdelete(repo, snap) ;
       errno = e ;
       strerr_warnfu4sys("atomically symlink ", newc + repolen + 10, " to ", fn) ;
       return -1 ;
     }
   }
+
   return 1 + !!oldc[repolen + 10] ;
 }
diff --git a/src/repo/s6rc_repo_setcopy.c b/src/repo/s6rc_repo_setcopy.c
new file mode 100644
index 0000000..30cb042
--- /dev/null
+++ b/src/repo/s6rc_repo_setcopy.c
@@ -0,0 +1,66 @@
+/* ISC license. */
+
+#include <string.h>
+#include <unistd.h>
+#include <errno.h>
+
+#include <skalibs/posixplz.h>
+#include <skalibs/djbunix.h>
+#include <skalibs/unix-transactional.h>
+
+#include <s6-rc/repo.h>
+
+static void cleanup (char const *s)
+{
+  int e = errno ;
+  rm_rf(s) ;
+  errno = e ;
+}
+
+int s6rc_repo_setcopy (char const *repo, char const *srcname, char const *dstname, unsigned int 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) return errno ;
+  }
+  else if (!(flags & 1)) return -1 ;
+
+  memcpy(realsrc, src, repolen + 9) ;
+  r = readlink(src, realsrc + repolen + 9, srclen + 9) ;
+  if (r == -1) return errno ;
+  if (r != srclen + 8) return -2 ;
+  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) return errno ;
+  if (!hiercopy(realsrc, realdst))
+  {
+    cleanup(realdst) ;
+    return errno ;
+  }
+  if (!atomic_symlink4(realdst + repolen + 9, dst, olddst + repolen + 9, dstlen + 9))
+  {
+    cleanup(realdst) ;
+    return errno ;
+  }
+  if (olddst[repolen + 9]) cleanup(olddst) ;
+  return 0 ;
+}
diff --git a/src/repo/s6rc_repo_setdelete.c b/src/repo/s6rc_repo_setdelete.c
new file mode 100644
index 0000000..a372d93
--- /dev/null
+++ b/src/repo/s6rc_repo_setdelete.c
@@ -0,0 +1,30 @@
+/* ISC license. */
+
+#include <string.h>
+#include <unistd.h>
+#include <errno.h>
+
+#include <skalibs/posixplz.h>
+#include <skalibs/djbunix.h>
+
+#include <s6-rc/repo.h>
+
+void s6rc_repo_setdelete (char const *repo, char const *set)
+{
+  size_t repolen = strlen(repo) ;
+  size_t setlen = strlen(set) ;
+  ssize_t r ;
+  char real[repolen + setlen + 18] ;
+  char fn[repolen + setlen + 11] ;
+  memcpy(fn, repo, repolen) ;
+  memcpy(fn + repolen, "/sources/", 9) ;
+  memcpy(fn + repolen + 9, set, setlen + 1) ;
+  if (access(fn, W_OK) == -1 && errno != ENOENT) return ;
+  memcpy(real, repo, repolen) ;
+  memcpy(real + repolen, "/sources/", 9) ;
+  r = readlink(fn, real + repolen + 9, setlen + 9) ;
+  if (r == -1 || r != setlen + 8) return ;
+  real[repolen + setlen + 17] = 0 ;
+  unlink_void(fn) ;
+  rm_rf(real) ;
+}