a8273be9da3b7a87a8d829d3efb79bce66e22039
angie
  Wed Jan 23 17:42:02 2019 -0800
New hg.conf settings sessionDataDir and sessionDataDbPrefix enable hgSession to move saved session trash files and customTrash tables into safe storage, so trash cleaner can be simpler.  refs #22440

When hgSession saves a session to namedSessionDb:
* If sessionDataDir is set in hg.conf (e.g. /data/apache/userdata on hgwdev), trash paths in cart variable values and in the contents of ctfile_$db and customComposite-$db files are replaced with paths in a directory hierarchy under sessionDataDir.  Files are moved from trash into the new directories and symlinks are made from trash locations to new locations.
* If sessionDataDbPrefix is set in hg.conf (e.g. customData), customTrash tables named in dbTableName settings in ctfile_$db are moved to a <sessionDataDbPrefix><dayOfMonth> database (e.g. customData03 on the third day of the month).  dbTableName settings are updated to point to the new locations.  If sessionDataDir is also set and a table contains a trash path, then the table is updated to contain to the new path under sessionDataDir.

sessionDataDir must be an absolute path to keep the symlinks straightforward.

The new directory hierarchy under sessionDataDir is A/B/C/D where A-D are defined as follows:
* A: the first two characters of the hex string md5sum of namedSessionDb.userName, i.e. the URI-encoded username truncated to varchar(32)
(there can be tens of thousands of userNames; using this mini-hash distributes them across up to 256 subdirectories of sessionDataDir)
* B: the URI-encoded userName
* C: the first 8 characters of the hex string md5sum of namedSessionDb.sessionName, i.e. the URI-encoded session name truncated to varchar(255)
* D: the original path below ../trash/

So, for example, the file ../trash/ct/ct_hgwdev_angie_11fc0_2b5970.maf could be moved to
/data/apache/userdata/fb/AngieHinrichs/cf2a2304/ct/ct_hgwdev_angie_11fc0_2b5970.maf

diff --git src/hg/inc/cart.h src/hg/inc/cart.h
index 755958c..9b2c11b 100644
--- src/hg/inc/cart.h
+++ src/hg/inc/cart.h
@@ -595,30 +595,34 @@
 int cartRemoveFromTdbTree(struct cart *cart,struct trackDb *tdb,char *suffix,boolean skipParent);
 /* Removes a 'trackName.suffix' from all tdb descendents (but not parent).
    If suffix NULL then removes 'trackName' which holds visibility */
 
 boolean cartTdbTreeReshapeIfNeeded(struct cart *cart,struct trackDb *tdbComposite);
 /* When subtrack vis is set via findTracks, and composite has no cart settings,
    then fashion composite to match found */
 
 boolean cartTdbTreeCleanupOverrides(struct trackDb *tdb,struct cart *newCart,struct hash *oldVars, struct lm *lm);
 /* When composite/view settings changes, remove subtrack specific settings
    Returns TRUE if any cart vars are removed */
 
 void cartCopyCustomComposites(struct cart *cart);
 /* Find any custom composite hubs and copy them so they can be modified. */
 
+void cartReplaceHubVars(struct cart *cart, char *hubFileVar, char *oldHubUrl, char *newHubUrl);
+/* Replace all cart variables corresponding to oldHubUrl (and/or its hub ID) with
+ * equivalents for newHubUrl. */
+
 void cgiExitTime(char *cgiName, long enteredMainTime);
 /* single stderr print out called at end of CGI binaries to record run
  * time in apache error_log */
 
 void cartHubWarn(char *format, va_list args);
 /* save up hub related warnings to put out later */
 
 void cartFlushHubWarnings();
 /* flush the hub errors (if any) */
 
 void cartCheckForCustomTracks(struct cart *cart, struct dyString *dyMessage);
 /* Scan cart for ctfile_<db> variables.  Tally up the databases that have
  * live custom tracks and those that have expired custom tracks. */
 /* While we're at it, also look for saved blat results. */