gitsvnversion-controlversion-control-keywords

Git keyword substitution like those in Subversion?


I used to work under Subversion/SVN and was instantly using nice feature called keyword substitution. Just putting in source files smth like:

/*
 *   $Author: ivanovpv $
 *   $Rev: 42 $
 *   $LastChangedDate: 2012-05-25 21:47:42 +0200 (Fri, 25 May 2012) $
 */

And each time Subversion was substituting keywords (Author, Rev, LastChangedDate) with actual ones.

Some time ago I was forced to move to Git and just wondering is there's something similar to Subversion's keyword substitution in Git?


Solution

  • Solution

    Well, you could easily implement such a feature yourself.

    Basically I embedded the commit command into a shell script. This script will first substitute the desired macros and then commit the changes. The project consists of two files:

    Content?

    keysub, a bash shell script and keysub.awk an awk script to replace keywords in a specific file. A third file is a config file which contains the values that should be substituted (besides variable stuff like commit count and timestamp).

    How do you use it?

    You call keysub instead of commit with the same options. The -m or -a option should come before any other commit option. A new option (that should always come first) is -f which takes a config file as a value. Example:

    $ git add 'someJavaFile.java'
    $ keysub -m 'fixed concurrent thread issue'
    $ git push
    

    or

    $ git -f .myfile.cnf -m 'enhanced javadoc entries'
    

    keysub

    #!/bin/bash
    
    # 0 -- functions/methods
    #########################
    # <Function description>
    function get_timestamp () {
      date    # change this to get a custom timestamp
    }
    
    # 1 -- Variable declarations
    #############################
    # input file for mapping
    file=".keysub.cnf"
    timestamp=$(get_timestamp)
    
    
    # 2 -- Argument parsing and flag checks
    ########################################
    
    # Parsing flag-list
    while getopts ":f:m:a" opt;
    do
      case $opt in
        f) file=${OPTARG}
           ;;
        a) echo 'Warning, keyword substitution will be incomplete when invoked'
           echo 'with the -a flag. The commit message will not be substituted into'
           echo 'source files. Use -m "message" for full substitutions.'
           echo -e 'Would you like to continue [y/n]? \c'
           read answer
           [[ ${answer} =~ [Yy] ]] || exit 3
           unset answer
           type="commit_a"
           break
           ;;
        m) type="commit_m"
           commitmsg=${OPTARG}
           break
           ;;
       \?) break
           ;;
      esac
    done
    shift $(($OPTIND - 1))
    
    # check file for typing
    if [[ ! -f ${file} ]]
    then
      echo 'No valid config file found.'
      exit 1
    fi
    
    # check if commit type was supplied
    if [[ -z ${type} ]]
    then
      echo 'No commit parameters/flags supplied...'
      exit 2
    fi
    
    # 3 -- write config file
    #########################
    sed "
      /timestamp:/ {
        s/\(timestamp:\).*/\1${timestamp}/
      }
      /commitmsg:/ {
        s/\(commitmsg:\).*/\1${commitmsg:-default commit message}/
      }
    " ${file} > tmp
    
    mv tmp ${file}
    
    # 4 -- get remaining tags
    ##########################
    author=$(grep 'author' ${file} | cut -f1 -d':' --complement)
    
    
    # 5 -- get files ready to commit
    #################################
    git status -s | grep '^[MARCU]' | cut -c1-3 --complement > tmplist
    
    # 6 -- invoke awk and perform substitution
    ###########################################
    # beware to change path to your location of the awk script
    for item in $(cat tmplist)
    do
      echo ${item}
      awk -v "commitmsg=${commitmsg}" -v "author=${author}" \
          -v "timestamp=${timestamp}" -f "${HOME}/lib/awk/keysub.awk" ${item} \
          > tmpfile
      mv tmpfile ${item}
    done
    rm tmplist
    
    # 5 -- invoke git commit
    #########################
    case ${type} in
      "commit_m") git commit -m "${commitmsg}" "$@"
                  ;;
      "commit_a") git commit -a "$@"
                  ;;
    esac
    
    # exit using success code
    exit 0
    

    keysub.awk

    # 0 BEGIN
    ##########
    BEGIN {
      FS=":"
      OFS=": "
    }
    
    # 1 parse source files 
    ########################
    # update author
    $0 ~ /.*\$Author.*\$.*/ {
      $2=author " $"
    }
    
    # update timestamp
    $0 ~ /.*\$LastChangedDate.*\$.*/ {
      $0=$1
      $2=timestamp " $"
    }
    
    # update commit message
    $0 ~ /.*\$LastChangeMessage.*\$.*/ {
      $2=commitmsg " $"
    }
    
    # update commit counts
    $0 ~ /.*\$Rev.*\$.*/ {
      ++$2
      $2=$2 " $"
    }
    
    # print line
    {
      print
    }
    

    Config file

    author:ubunut-420
    timestamp:Fri Jun 21 20:42:54 CEST 2013
    commitmsg:default commit message
    

    Remarks

    I've tried to document well enough so you can easily implement it and modify it to your own, personal needs. Note that you can give the macros any name you want to, as long as you modify it in the source code. I also aimed to keep it relatively easy to extend the script, you should be able to add new macros fairly easily. If you're interested in extending or modifying the script, you might want to take a look at the .git directory too, there should be plenty of info there that can help to enhance the script, due to lack of time I didn't investigate the folder though.