On 23/03/2022 20:25, Taylor Blau wrote:
On Wed, Mar 23, 2022 at 03:19:06PM +0000, John Garry wrote:
For building the linux perf tool we use the git head commit id as part of
the tool version sting. To save time in re-building, the Makefile rule has a
dependency on .git/HEAD for rebuilding. An alternative approach would be to
compare git log output to check current versus previous build head commit,
but that is seen as inefficient time-wise.
Having a Makefile recipe that depends on $GIT_DIR/HEAD seems strange to
me.
Yeah, as mentioned, the idea was the we can check a rebuild on this
rather than running a relatively time-consuming command like "git
describe". Wasn't my idea :)
Presumably your Makefile rules would map out which parts of your program
depend on each other, and would get invalidated when the source itself
changes, no?
Correct, they do. It's just the part which constructs the app version
tag which depends on this.
Perhaps you also care about the commit you're building from in order to
embed something into your program. But it seems like you could inject
the output of "git rev-parse HEAD" when you construct the version
identifier whenever you do need to rebuild.
ok, so I think that we may need to run a git command always one way or
another.
Thanks,
John
