cachevfs: use a compatibility later for all access

diff: drop default argument value This argument use the default value for an argument not available in earlier version. So we just stop passing the argument.

test: use hash in test-evolve-topic.t This helps testing compat with older version.

packaging: prepare version 7.2.0

changelog: prepare for coming release

stablerange: add missing licence and copyright header

obshistory: pass the csets description in getmarkerdescriptionpatch Previous patches removed any use of ctx in the function and we now just need the cset description in the function. Let's pass that only. This will save couple of calls of repo[node].

obshistory: remove the unused function The function is not used anymore.

obslog: add header to the changeset description diff This patch adds `diff -r <hash> -r <hash> <filename>` header to the output of the changeset description diff which is shown using the --patch flag of obslog command. This fixes the label/color issue for description diff also.

obslog: colorize the description diff shown in obslog -p This patch colorizes the description diff shown in `hg obslog -p`. The labels for the header are different from that of the patch as the main header which says `diff -r <somehash> -r <somehash> <filename>`. Next patch will hack to add that.