using branch approach to calculate version when not directly tagged.

Then, it will be something like this:
- tagged versions will be called: Pharo7.0.0-rc2* (for example)
- non tagger versions will be called: Pharo7.0-SNAPSHOT* (for example)

bootstrap/scripts/4-build.sh

@@ -8,6 +8,12 @@ set -e
 SCRIPTS="$(cd "$(dirname "${BASH_SOURCE[0]}")" ; pwd -P)"
 . ${SCRIPTS}/envvars.sh
 
+if [ $(is_version) == 1 ]; then
+    PHARO_NAME_PREFIX=${PHARO_VERSION_PREFIX}
+else
+    PHARO_NAME_PREFIX=${PHARO_SNAPSHOT_PREFIX}
+fi
+
 # A POSIX variable
 OPTIND=1         # Reset in case getopts has been used previously in the shell.
 

bootstrap/scripts/envversion.sh

@@ -5,8 +5,22 @@
 # - current image version prefix, e.g. "Pharo7.0.0-rc1"
 # - vm version for the current image, to be used to download the correct vm, e.g. "70"
 
+# Versions are taken from tags. Tag should have a format like vMAJOR.MINOR.PATCH[-EXTRA], e.g. v7.0.0-rc1
+PHARO_VERSION_PREFIX="Pharo`git describe --long --tags | cut -d'-' -f 1-2 | cut -c 2-`"
+# Snapshots are taken from branchs. Branchs should be named dev-MAJOR.MINOR (example: dev-7.0)
+PHARO_SNAPSHOT_PREFIX="Pharo`git branch | grep \* | cut -d' ' -f 2 | cut -d'-' -f 2`-SNAPSHOT"
 
-PHARO_NAME_PREFIX="Pharo`git describe --long --tags | cut -d'-' -f 1-2 | cut -c 2-`"
-PHARO_SHORT_VERSION=`git describe --long --tags | cut -d'-' -f 1 | cut -c 2- | cut -d'.' -f 1-2 | sed 's/\.//'`
+PHARO_SHORT_VERSION=`git branch | grep \* | cut -d' ' -f 2 | cut -d'-' -f 2 | sed 's/\.//'`
 # this is just to make things clear (and because they could change in the future, who knows :P)
-PHARO_VM_VERSION="${PHARO_SHORT_VERSION}"
+PHARO_VM_VERSION="${PHARO_SHORT_VERSION}"
+
+# use this to know if we are in a version or a SNAPSHOT
+function is_version() {
+	set -f
+	local versionTag=$(git tag --list --points-at HEAD | grep -E "^v[0-9]+\.[0-9]+.[0-9]+(\-[a-zA-Z0-9_]+)?$")
+    if [ "${versionTag}" == "" ]; then
+        echo 0
+    else
+        echo 1
+    fi
+}