[PATCH] buildhistory.bbclass: remove out-dated information on request

[Patrick Ohly <patrick.ohly@intel.com>]

buildhistory.bbclass by design is incremental: each build adds or
updates information. Information is never removed.

Sometimes it can be useful to reduce the information only to those
recipes that were build during a specific bitbake invocation, for
example when the invocation does a full world build.

This is now possible by invoking bitbake with:
   BB_ENV_EXTRAWHITE=BUILDHISTORY_REMOVE_OLD BUILDHISTORY_REMOVE_OLD=1 bitbake

In this mode, buildhistory.bbclass first moves all existing
information into a temporary directory called "old" inside the build
history directory. There the information is used for the "version
going backwards QA check". Then when the build is complete and before
(potentially) committing to git, the temporary directory gets deleted.

Because information that has not changed during the build will be
reconstructed, a git log will then only show real updates, additions
and removals.

Signed-off-by: Patrick Ohly <patrick.ohly@intel.com>
---
 meta/classes/buildhistory.bbclass | 43 +++++++++++++++++++++++++++++++--------
 1 file changed, 34 insertions(+), 9 deletions(-)

diff --git a/meta/classes/buildhistory.bbclass b/meta/classes/buildhistory.bbclass
index 3c4647a..1fadd2e 100644
--- a/meta/classes/buildhistory.bbclass
+++ b/meta/classes/buildhistory.bbclass
@@ -11,6 +11,12 @@ BUILDHISTORY_FEATURES ?= "image package sdk"
 BUILDHISTORY_DIR ?= "${TOPDIR}/buildhistory"
 BUILDHISTORY_DIR_IMAGE = "${BUILDHISTORY_DIR}/images/${MACHINE_ARCH}/${TCLIBC}/${IMAGE_BASENAME}"
 BUILDHISTORY_DIR_PACKAGE = "${BUILDHISTORY_DIR}/packages/${MULTIMACH_TARGET_SYS}/${PN}"
+# Setting this to non-empty will remove the old content of the buildhistory as part of
+# the current bitbake invocation and replace it with information about what was built
+# during the build.
+BUILDHISTORY_REMOVE_OLD ?= ""
+BUILDHISTORY_OLD_DIR = "${BUILDHISTORY_DIR}/${@ "old" if "${BUILDHISTORY_REMOVE_OLD}" else ""}"
+BUILDHISTORY_OLD_DIR_PACKAGE = "${BUILDHISTORY_OLD_DIR}/packages/${MULTIMACH_TARGET_SYS}/${PN}"
 BUILDHISTORY_DIR_SDK = "${BUILDHISTORY_DIR}/sdk/${SDK_NAME}${SDK_EXT}/${IMAGE_BASENAME}"
 BUILDHISTORY_IMAGE_FILES ?= "/etc/passwd /etc/group"
 BUILDHISTORY_SDK_FILES ?= "conf/local.conf conf/bblayers.conf conf/auto.conf conf/locked-sigs.inc conf/devtool.conf"
@@ -49,6 +55,7 @@ python buildhistory_emit_pkghistory() {
     import errno
 
     pkghistdir = d.getVar('BUILDHISTORY_DIR_PACKAGE', True)
+    oldpkghistdir = d.getVar('BUILDHISTORY_OLD_DIR_PACKAGE', True)
 
     class RecipeInfo:
         def __init__(self, name):
@@ -139,7 +146,7 @@ python buildhistory_emit_pkghistory() {
 
     def getlastpkgversion(pkg):
         try:
-            histfile = os.path.join(pkghistdir, pkg, "latest")
+            histfile = os.path.join(oldpkghistdir, pkg, "latest")
             return readPackageInfo(pkg, histfile)
         except EnvironmentError:
             return None
@@ -722,17 +729,35 @@ END
 
 python buildhistory_eventhandler() {
     if e.data.getVar('BUILDHISTORY_FEATURES', True).strip():
-        if e.data.getVar("BUILDHISTORY_COMMIT", True) == "1":
-            bb.note("Writing buildhistory")
-            localdata = bb.data.createCopy(e.data)
-            localdata.setVar('BUILDHISTORY_BUILD_FAILURES', str(e._failures))
-            interrupted = getattr(e, '_interrupted', 0)
-            localdata.setVar('BUILDHISTORY_BUILD_INTERRUPTED', str(interrupted))
-            bb.build.exec_func("buildhistory_commit", localdata)
+        remove = e.data.getVar("BUILDHISTORY_REMOVE_OLD", True)
+        olddir = e.data.getVar("BUILDHISTORY_OLD_DIR", True)
+        if isinstance(e, bb.event.BuildStarted):
+            if remove:
+                import shutil
+                # Clean up after potentially interrupted build.
+                if os.path.isdir(olddir):
+                    shutil.rmtree(olddir)
+                rootdir = e.data.getVar("BUILDHISTORY_DIR", True)
+                entries = [ x for x in os.listdir(rootdir) if not x.startswith('.') ]
+                bb.utils.mkdirhier(olddir)
+                for entry in entries:
+                    os.rename(os.path.join(rootdir, entry),
+                              os.path.join(olddir, entry))
+        elif isinstance(e, bb.event.BuildCompleted):
+            if remove:
+                import shutil
+                shutil.rmtree(olddir)
+            if e.data.getVar("BUILDHISTORY_COMMIT", True) == "1":
+                bb.note("Writing buildhistory")
+                localdata = bb.data.createCopy(e.data)
+                localdata.setVar('BUILDHISTORY_BUILD_FAILURES', str(e._failures))
+                interrupted = getattr(e, '_interrupted', 0)
+                localdata.setVar('BUILDHISTORY_BUILD_INTERRUPTED', str(interrupted))
+                bb.build.exec_func("buildhistory_commit", localdata)
 }
 
 addhandler buildhistory_eventhandler
-buildhistory_eventhandler[eventmask] = "bb.event.BuildCompleted"
+buildhistory_eventhandler[eventmask] = "bb.event.BuildCompleted bb.event.BuildStarted"
 
 
 # FIXME this ought to be moved into the fetcher
-- 
2.1.4