GENVER

#!/bin/bash

# GENVER returns a semantic version of the current branch.
#
# It generates the semantic version based on the tag references on 
# the repo.
#
# Args: 
#   Can pass "--pep440" to generate PEP-440 compliant version 
#
# Assumptions:
#   - Will match only tags matching "v[0-9]*" (e.g., v0.0.1)
#   - Repo owners tag accordingly per release
#
# Example:
#
#   1. If the latest tag (v0.0.1) is at HEAD~4 and HEAD is at commit 60f987bf,
#      running
#
#        ./GENVER --pep440
#
#      will return: 0.0.1.dev4+g60f987bfd 
#
#      NOTE: PyPI will not allow these local versions to be pushed: "Can't use
#            PEP 440 local versions. See https://packaging.python.org/specifications/core-metadata
#            for more information."
#
#   2. If "--pep440" is not passed into example (1), it would return 0.0.1-4.g60f987bfd 
#
#   3. If the latest tag (v0.0.2) is at HEAD of branch (60f987bf), it'll
#      treat it as a released state, so running:
#
#        ./GENVER --pep440
#
#      will return: 0.0.2
#


set -e

# Generates a PEP 440 compatible version instead of a semantic version.
if test "$1" = "--pep440"; then
    GENVER_PEP440="true"
fi

# Dependency checks.
dependencies="cat expr git"
for cmd in ${dependencies}; do
    if ! command -v "${cmd}" >/dev/null 2>&1; then
        >&2 echo "Command ${cmd} is unavailable."
        exit 1
    fi
done

# Validate the candidate version.
ROOT=$(git rev-parse --show-toplevel)
VERSION_FILE="${ROOT}/VERSION"

if test -f "${VERSION_FILE}"; then
    can_ver=$(cat "${VERSION_FILE}")
else
    >&2 echo "Error: Failed to find the VERSION file, please refer to RELEASE.md" \
             "as we reference VERSION file for the base candidate version."
    exit 1
fi

# Get the "git describe" version.
# Normal case, the versioning tags looks like "v1.0.0", "v1.0.1",...
if ! git_ver=$(git describe --tags --abbrev=9 --match "v[0-9]*" HEAD 2>/dev/null)
then
    >&2 echo "Error: Can't get any versioning tag. Are tags pushed?"
fi

# Strip the leading 'v' from the git describe version.
git_ver=$(expr "${git_ver}" : v*'\(.*\)')

if expr "${git_ver}" : '.*-[0-9]*-g.*'  >/dev/null
then 
    # Branch is in the developing state (e.g., there have been commits
    # since the last tag).

    # Extract each part of the "git describe" version.
    tag_ver=$(expr "$git_ver" : '\(.*\)-[0-9]*-g.*')
    commit_count=$(expr "$git_ver" : '.*-\([0-9]*\)-g.*')
    commit_hash=$(expr "$git_ver" : '.*-[0-9]*-\(g.*\)')

    if test "$can_ver" = "$tag_ver"
    then
        >&2 echo "Error: The candidate version on this branch is still at" \
                 "what has been released. You can pull in latest VERSION file" \
                 "to be up-to-date"
        exit 1
    fi

    if test "${GENVER_PEP440:-}" = "true"
    then
        sem_ver="${tag_ver}.dev${commit_count}+${commit_hash}"
    else
        # Generate the semantic version for pre-release.
        # Case 1 (candidate version contains hyphen):
        #    candidate version(VERSION file) : 1.0.0-p1
        #                                      ========
        #    git describe returns            : 1.0.0-2-gde2198c
        #                                           ~~~~~~~~~~~
        #    semantic version(generated)     : 1.0.0-p1.2.gde2198c
        #                                      ========~~~~~~~~~~~
        #                                              ^ ^
        # Case 2:
        #    candidate version(VERSION file) : 1.0.1
        #                                      =====
        #    git describe returns            : 1.0.0-2-gde2198c
        #                                           ~~~~~~~~~~~
        #    semantic version(generated)     : 1.0.1-2.gde2198c
        #                                      =====~~~~~~~~~~~
        #                                             ^
        if expr "$tag_ver" : ".*-" >/dev/null
        then
            sem_ver="${tag_ver}.${commit_count}.${commit_hash}"
        else
            sem_ver="${tag_ver}-${commit_count}.${commit_hash}"
        fi
    fi

else
   # Branch is in the released state.
   # Use the version taken from tag as-is
   sem_ver="${git_ver}"
fi

echo "${sem_ver}"