[R-pkg-devel] *not* re-making package if contents haven't changed

[Greg Minshall]

hi.  i use emacs org-mode to write my literate (semi-, in my case)
code.  then, 'tangle' the results into package/R/foo.R, etc.

the tangling is driven by a makefile.  (my methodology is to make the
package source tree as a subdirectory of where my makefile sits; i
realize this is non-standard, and in many respects sub-optimal.)

the makefile then proceeds to R-CMD-build, R-CMD-check, and, assuming
those pass, Rscript-install the package.

i would like to *not* do the build/check/install if, in fact, nothing
has changed in the tangled files since the last time the
build/check/install ran.  the *dates* of the files (which is what make
typically looks at) *will* have changed.  but, i want to rely on the
contents, not on the dates.

i can imagine various hacks to accomplish this.  but, i thought that
someone on the list may have run into this before and have a
recommendation.

if so, i'm all ears!  thanks in advance.

cheers, Greg