[petsc-dev] Bash tool for handling switching between multiple PETSc branches and configures

[Smith, Barry F.]

   A long time ago Oana suggested a tool that allowed switching between PETSc configurations after pulls etc that didn't require waiting to recompile code or rerun configure. Based on her ideas I finally got something that has been behaving reasonably satisfactory for me. Note that it is only useful if you work with PETSc in a way that you have multiple branches and PETSc arches you are dealing with. If you are essentially always in one branch it offers no advantages. (Unfortunately since Fortran stubs are stored in the source for branch changes that 
change the stubs the will require recompiles). This is my first public release so may have glitches. It saves me tons of time. 

   Put this in your .bashrc file and run source ~/.bashrc  Docs are at the bottom.

#
#  Utility function used by gitcheckout bash function
#    uses the basename of the branch to build the PETSC_ARCH
#
function branchtoarch () {
    basename `echo $1 | sed s?/maint?-maint?g` | sed -e s?/?-?g -e s?^?arch-?g
}

#
# Used by the git alias provided below; not used directly
#
# Implements a git checkout, but preserves any previously compiled (.o) code so it won't unneccessariy get recompiled
#
# Sets PETSC_ARCH automatically based on the branch name
#
# How it works:
#    1) before changing from the current PETSC_ARCH branch combination it deletes all out-dated .o files for that PETSC_ARCH (using make --dry-run to find these)
#    2) after checking into the new PETSC_ARCH branch combination it updates the time-stamps of all remaing .o files for the new PETSC_ARCH so they are
#       more recent than any timestamps on the source files that git may have changed (it can do this because it knows from 1) that any out-of-date
#       .o files have already been deleted)
#
#   Does not change the timestamps or touch in any way the source code, only .o files
#
function gitcheckout {
    new_branch=$1
    current_branch=`command git rev-parse --abbrev-ref HEAD`

    if [ -f ${new_branch} ]; then
      command git checkout ${new_branch}
      return 0
    fi

    if [ "${new_branch}" == "-b" ]; then
      command git rev-parse --verify $2 > /dev/null  2>&1
      if [ "$?" == "0" ]; then
        echo "Branch you are trying to create $2 already exists, aborting"
        return 9
      else
        # create the new branch, do not yet check it out
        new_branch=$2
        command git branch ${new_branch}
      fi
    else
      if [ "${current_branch}" == "${new_branch}" ]; then
        echo "Already in branch ${new_branch}"
        return 0
      fi
      changes=`command git status --untracked-files=no --porcelain`
      if [ "${changes}" != "" ]; then
        echo "You have modified or new files; not changing branches"
        echo ${changes}
        return 5
      fi
    fi

    current_arch=`branchtoarch ${current_branch}`
    new_arch=`branchtoarch ${new_branch}`

    isbranch=0
    command git rev-parse --verify ${new_branch} > /dev/null  2>&1
    if [ "$?" == "0" ]; then
      isbranch=1
    else
      command git rev-parse --verify origin/${new_branch} > /dev/null  2>&1
      if [ "$?" == "0" ]; then
        isbranch=1
      fi
    fi
    if [ "${isbranch}" == "0" ]; then
      echo "Branch ${new_branch} does not exist"
      return 3
    fi

    echo "Checking out branch ${new_branch} and PETSC_ARCH ${new_arch}"

    if [ "${PETSC_ARCH}" != "${current_arch}" ]; then
      echo "Current PETSC_ARCH ${PETSC_ARCH} not equal to expected value ${current_arch} unable to removed out-dated object files"
    else
      #  delete all out-dated .o files
      if [[ -f ${PETSC_DIR}/${PETSC_ARCH}/lib/petsc/conf/petscvariables && -d ${PETSC_DIR}/${PETSC_ARCH}/obj ]]; then
        pushd ${PETSC_DIR}
        make --dry-run -f gmakefile  | sed -n 's?[[:print:][:cntrl:]]*-o[[:blank:]]\([-[:alpha:]/]*\.o\)[[:print:][:cntrl:]]*?\1?gp' | xargs rm -f
        popd
      fi
    fi

    command git checkout ${new_branch}
    if [ "$?" != "0" ]; then
      echo "Unable to checkout branch ${new_branch}"
      return 4
    fi

    export PETSC_ARCH=${new_arch}
    #  update the timestamps of all .o that remain for this PETSC_ARCH and the library
    if [[ -f ${PETSC_DIR}/${PETSC_ARCH}/lib/petsc/conf/petscvariables && -d ${PETSC_DIR}/${PETSC_ARCH}/obj ]]; then
      find ${PETSC_DIR}/${PETSC_ARCH}/obj -type f -name *.o -exec touch -m {} +
      touch -m ${PETSC_DIR}/${PETSC_ARCH}/lib/libpetsc*
#      /usr/bin/dsymutil libpetsc.3.011.3.dylib
    fi
}

#
#  An alias for git checkout that manages resetting the PETSC_ARCH to the branch name and preserving compiled code associated with the branch checked out
#
#  Oana suggested the idea to save waiting for code to recompile after changing branches and the use of touch to force code to not get recompiled unnecessarily
#
#  Usage:
#     git checkout branchname
#
#  Examples:
#      $ git checkout next
#          Checking out branch next and PETSC_ARCH arch-none
#          Switched to branch 'next'
#          ~/Src/petsc (next<) arch-next
#
#      $ git checkout master
#          Checking out branch master and PETSC_ARCH arch-master
#          Switched to branch 'master'
#          ~/Src/petsc (master=) arch-master
#
#      $ git checkout -b barry/mynewbranch
#           Switched to branch 'barry/mynewbranch'
#           ~/Src/petsc (barry/mynewbranch=) arch-mynewbranch
#
# Uses the bash function gitcheckout
#
function git {
  groot=`command git rev-parse --absolute-git-dir 2> /dev/null`
  if [[ "$1" == "checkout" && "$@" != *"--help"* && "${PETSC_DIR}" != "" && "${PETSC_DIR}/.git" == "${groot}" ]]; then
    shift 1
    if [ "$1" == "git" ]; then
      shift 2
    fi
    gitcheckout "$@"
  else
    command git "$@"
  fi
}