revert.c

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/************************************************************************
 * Copyright (C) 2006-2009 Philipp Marek.
 *
 * This program is free software;  you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 3 as
 * published by the Free Software Foundation.
 ************************************************************************/
#include <unistd.h>
#include <stdio.h>
#include <fcntl.h>
#include <time.h>

#include <subversion-1/svn_delta.h>
#include <subversion-1/svn_ra.h>

#include "revert.h"
#include "waa.h"
#include "est_ops.h"
#include "racallback.h"
#include "warnings.h"
#include "resolve.h"
#include "checksum.h"
#include "props.h"
#include "helper.h"
#include "url.h"
#include "update.h"
#include "cp_mv.h"
#include "status.h"


enum rev___dir_change_flag_e {
    NOT_CHANGED=0,
    REVERT_MTIME=1,
    SET_CURRENT=2,
    GET_TSTAMP=0x1000,
};

 
static int number_reverted=0;
static svn_revnum_t last_rev;


#define REV___GETFILE_MAX_CACHE (4)


int rev__get_text_to_stream( char *loc_url, svn_revnum_t revision,
        const char *decoder,
        svn_stream_t *output,
        struct estat *sts_for_manber,
        struct estat *output_sts,
        apr_hash_t **props,
        apr_pool_t *pool)
{
    int status;
    svn_error_t *status_svn;
    svn_string_t *prop_val;
    struct encoder_t *encoder;
    char *relative_url, *utf8_url;
    apr_hash_t *properties;
    char target_rev[10];


    encoder=NULL;
    status=0;
    DEBUGP("getting file %s@%s from %s", loc_url, 
            hlp__rev_to_string(revision), current_url->url);


    if (strncmp(loc_url, "./", 2) == 0)
    {
        /* Skip ./ in front. */
        relative_url=loc_url+2;
    }
    else
    {
        /* It could be an absolute value. */

        /* Verify that the correct URL is taken.
         * The "/" that's not stored at the end of the URL must be there, too.  
         * */
        if (strncmp(current_url->url, loc_url, current_url->urllen) == 0 &&
                loc_url[current_url->urllen] == '/')
            loc_url += current_url->urllen+1;

        /* If the string doesn't match, it better be a relative value already 
         * ... else we'll get an error.  */
        //  else STOPIF(EINVAL, "%s not below %s", loc_url, current_url->url);
    }

    STOPIF( hlp__local2utf8(loc_url, &utf8_url, -1), NULL);


    /* Symlinks have a MD5, too ... so just do that here. */
    /* How do we get the filesize here, to determine whether it's big
     * enough for manber block hashing? */
    /* Short answer: We don't.
     * We need to get the MD5 anyway; there's svn_stream_checksummed(),
     * but that's just one chainlink more, and so we simply use our own
     * function. */
    if (sts_for_manber)
        STOPIF( cs__new_manber_filter(sts_for_manber, 
                    output, &output, pool), NULL);  


    /* If there's a fsvs:update-pipe, we would know when we have the file 
     * here - which is a bit late, because we'd have to read/write the entire 
     * file afresh. So we remember the property in the cb__record_changes() 
     * call chain, and look for the string here. 
     *
     * But that works only if we *know* that we're processing the right 
     * version. If the filter changed for this file, we might try to decode 
     * with the wrong one - eg. for diff, where multiple versions are handled 
     * in a single call.
     * 
     * We know that we have the correct value locally if the wanted revision 
     * is the same as we've in the entry; if they are different, we have to 
     * ask the repository for the data.
     *
     *
     * Note: we're trading network-round-trips for local disk bandwidth.
     * The other way would be to fetch the data encoded, *then* look in the 
     * properties we just got for the pipe-command, and re-pipe the file 
     * through the command given.
     *
     * But: the common case of updates uses cb__record_changes(), which 
     * already gets the correct value. So in this case we need not look any 
     * further.
     */
    /* \todo For things like export we could provide a commandline parameter; 
     * use network, or use disk.
     * For a local-remote diff we could pipe the data into the diff program; 
     * but that wouldn't work for remote-remote diffing, as diff(1) doesn't 
     * accept arbitrary filehandles as input (and /proc/self/fd/ isn't 
     * portable). */

    /* Fetch decoder from repository. */
    if (decoder == DECODER_UNKNOWN)
    {
        STOPIF_SVNERR_TEXT( svn_ra_get_file,
                (current_url->session,
                 loc_url, revision,
                 NULL,
                 &revision, &properties,
                 pool),
             "Fetching entry \"%s/%s\"@%s", 
             current_url->url,
             loc_url, hlp__rev_to_string(revision));

        prop_val=apr_hash_get(properties, propval_updatepipe, APR_HASH_KEY_STRING);
        decoder=prop_val ? prop_val->data : NULL;
    }


    /* First decode, then do manber-hashing. As the filters are prepended, we 
     * have to do that after the manber-filter. */
    if (decoder)
    {
        snprintf(target_rev, sizeof(target_rev), 
                "%llu", (t_ull)revision);
        setenv(FSVS_EXP_TARGET_REVISION, target_rev, 1);

        STOPIF( hlp__encode_filter(output, decoder, 1, 
                    loc_url, &output, &encoder, pool), NULL);
        if (output_sts)
            encoder->output_md5= &(output_sts->md5);
    }


    STOPIF_SVNERR_TEXT( svn_ra_get_file,
            (current_url->session,
             loc_url, revision,
             output,
             &revision, &properties,
             pool),
            "Fetching entry %s/%s@%s",  
            current_url->url,
            loc_url, hlp__rev_to_string(revision));
    DEBUGP("got revision %llu", (t_ull)revision);

    /* svn_ra_get_file doesn't close the stream. */
    STOPIF_SVNERR( svn_stream_close, (output));
    output=NULL;

    if (output_sts)
    {
        output_sts->repos_rev = revision;
        STOPIF( prp__set_from_aprhash( output_sts, properties, 
                    ONLY_KEEP_USERDEF, NULL, pool), NULL);
    }

    if (props)
        *props=properties;


ex:
    return status;
}


int rev__get_text_to_tmpfile(char *loc_url, svn_revnum_t revision,
        char *encoder,
        char *filename_base, char **filename,
        struct estat *sts_for_manber, 
        struct estat *output_sts, apr_hash_t **props,
        apr_pool_t *pool)
{
    int status;
    apr_file_t *apr_f;
    svn_stream_t *output;


    status=0;

    STOPIF( waa__get_tmp_name( filename_base, filename, &apr_f, pool), NULL);
    output=svn_stream_from_aprfile(apr_f, pool);

    STOPIF( rev__get_text_to_stream( loc_url, revision, encoder,
                output, sts_for_manber, output_sts, props, pool), NULL);

    /* svn_ra_get_file() doesn't close. */
    STOPIF( apr_file_close(apr_f), NULL);

ex:
    return status;
}


int rev__get_text_into_buffer(char *loc_url, svn_revnum_t revision,
        const char *decoder,
        svn_stringbuf_t **output,
        struct estat *sts_for_manber,
        struct estat *output_sts,
        apr_hash_t **props,
        apr_pool_t *pool)
{
    int status;
    svn_stringbuf_t *string;
    svn_stream_t *stream;

    status=0;
    string=svn_stringbuf_create("", pool);
    stream=svn_stream_from_stringbuf(string, pool);

    STOPIF( rev__get_text_to_stream(loc_url, revision,
                decoder, stream, sts_for_manber, output_sts, props, pool), NULL);

    *output=string;
ex:
    return status;
}


int rev__install_file(struct estat *sts, svn_revnum_t revision,
        char *decoder,
        apr_pool_t *pool)
{
    int status;
    char *filename;
    char *filename_tmp;
    apr_hash_t *props;
    svn_stream_t *stream;
    apr_file_t *a_stream;
    apr_pool_t *subpool;
    char *special_data;
    char *url;
    svn_revnum_t rev_to_take;


    BUG_ON(!pool);
    STOPIF( ops__build_path(&filename, sts), NULL);


    /* We know that we have to do something here; but because the order is 
     * depth-first, the parent directory isn't done yet (and shouldn't be, 
     * because it needs permissions and mtime set!).
     * So it's possible that the target directory doesn't yet exist.
     *
     * Note: because we're here for *non-dir* entries, we always have a 
     * parent. */
    STOPIF( waa__mkdir(filename, 0), NULL);


    STOPIF( apr_pool_create(&subpool, pool),
            "Creating the filehandle pool");


    /* When we get a file, old manber-hashes are stale.
     * So remove them; if the file is big enough, we'll recreate it with 
     * correct data. */
    STOPIF( waa__delete_byext(filename, WAA__FILE_MD5s_EXT, 1), NULL);


    /* Files get written in files; we use the temporarily generated name for  
     * special entries, too. */
    /* We could use a completely different mechanism for temp-file-names;
     * but keeping it close to the target lets us see if we're out of
     * disk space in this filesystem. (At least if it's not a binding mount
     * or something similar - but then rename() should fail).
     * If we wrote the data somewhere else, we'd risk moving it again, across 
     * filesystem boundaries. */
    STOPIF( waa__get_tmp_name( filename, &filename_tmp, &a_stream, subpool), 
            NULL);


    /* It's a bit easier to just take the (small) performance hit, and always 
     * (temporarily) write the data in a file.
     * If it's a special entry, that will just get read immediately back and 
     * changed to the correct type.
     *
     * It doesn't really make much difference, as the file is always created 
     * to get a distinct name. */
    stream=svn_stream_from_aprfile(a_stream, subpool);


    if (sts->url)
    {
        STOPIF( hlp__local2utf8( filename+2, &url, -1), NULL);
        rev_to_take=sts->repos_rev;
        current_url=sts->url;
    }
    else if (sts->flags & RF___IS_COPY)
    {
        STOPIF( cm__get_source( sts, filename, &url, &rev_to_take, 0), NULL);
        STOPIF( url__find( url, &current_url), NULL);
        STOPIF( hlp__local2utf8( url, &url, -1), NULL);
    }
    else
        BUG("cannot get file %s", filename);

    if (revision == 0) 
    {
        /* BASE wanted; get decoder. */
        STOPIF( up__fetch_decoder(sts), NULL);
        decoder=sts->decoder;
    }
    else
    {
        /* Arbitrary revision - get decoder. */
        rev_to_take=revision;
        decoder=DECODER_UNKNOWN;
    }


    STOPIF( url__open_session(NULL, NULL), NULL);

    /* We don't give an estat for meta-data parsing, because we have to loop 
     * through the property list anyway - for storing locally. */
    STOPIF( rev__get_text_to_stream( url, rev_to_take, decoder, 
                stream, sts, NULL, &props, pool), NULL);


    if (apr_hash_get(props, propname_special, APR_HASH_KEY_STRING))
    {
        STOPIF( ops__read_special_entry( a_stream, &special_data, 
                    0, NULL, filename_tmp, subpool), NULL);

        /* The correct type gets set on parsing. */
        STOPIF( up__handle_special(sts, filename_tmp, 
                    special_data, subpool), NULL);
    }
    else
    {
        /* If it's not special, it must be an ordinary file. */
        /* This is a kind of default value, the mode is set to the repository 
         * value in up__set_meta_data(). */
        sts->st.mode = (sts->st.mode & ~S_IFMT) | S_IFREG;
        sts->local_mode_packed=sts->new_rev_mode_packed=
            MODE_T_to_PACKED(sts->st.mode);
    }


    STOPIF( prp__set_from_aprhash(sts, props, STORE_IN_FS, 
                NULL, subpool), NULL);


    /* We write all meta-data. If we got no values from the repository, we just
     * write what we have in the local filesystem back - the temporary file has
     * just some default values, after all. */
    sts->remote_status |= FS_META_CHANGED;
    DEBUGP("setting meta-data");
    STOPIF( up__set_meta_data(sts, filename_tmp), NULL);

    STOPIF( apr_file_close(a_stream), NULL);


    DEBUGP("rename to %s", filename);
    /* rename to correct filename */
    STOPIF_CODE_ERR( rename(filename_tmp, filename)==-1, errno,
            "Cannot rename '%s' to '%s'", filename_tmp, filename);

    /* The rename changes the ctime. */
    STOPIF( hlp__lstat( filename, &(sts->st)),
            "Cannot lstat('%s')", filename);


    sts->url=current_url;
    /* We have to re-sort the parent directory, as the inode has changed
     * after an rename(). */
    sts->parent->to_be_sorted=1;

    apr_pool_destroy(subpool);
    subpool=NULL;


ex:
    /* On error remove the temporary file. */
    /* Return the original error. */
    if (status)
        unlink(filename_tmp);

    return status;
}


int rev__merge(struct estat *sts,
        const char *file1, 
        const char *common, 
        const char *file2)
{
    int status;
    pid_t pid;
    char *output;
    int hdl;
    struct sstat_t stat;
    int retval;


    STOPIF( ops__build_path(&output, sts), NULL);

    /* Remember the meta-data of the target */
    STOPIF( hlp__lstat(file2, &stat), NULL);


    pid=fork();
    STOPIF_CODE_ERR( pid == -1, errno, "Cannot fork()" );
    if (pid == 0)
    {
        /* Child. */
        /* TODO: Is there some custom merge program defined?
         * We always use the currently defined property. */
        /* TODO: how does that work if an update sends a wrong property? use 
         * both? */

        /* Open the output file. */
        hdl=open(output, O_WRONLY | O_CREAT, 0700);
        STOPIF_CODE_ERR( hdl == -1, errno, 
                "Cannot open merge output \"%s\"", output);
        STOPIF_CODE_ERR( dup2(hdl, STDOUT_FILENO) == -1, errno,
                "Cannot dup2");
        /* No need to close hdl -- it's opened only for that process, and will 
         * be closed when it exec()s. */

        /* Remove the ./ at the front */
        setenv(FSVS_EXP_CURR_ENTRY, output+2, 1);

        STOPIF_CODE_ERR( execlp( opt__get_string(OPT__MERGE_PRG), 
                    opt__get_string(OPT__MERGE_PRG),
                    opt__get_string(OPT__MERGE_OPT),
                    file1, common, file2,
                    NULL) == -1, errno,
                "Starting the merge program \"%s\" failed",
                opt__get_string(OPT__MERGE_PRG));

    }

    STOPIF_CODE_ERR( pid != waitpid(pid, &retval, 0), errno, "waitpid");

    DEBUGP("merge returns %d (signal %d)", 
            WEXITSTATUS(retval), WTERMSIG(retval));

    /* Can that be? */
    STOPIF_CODE_ERR( WIFSIGNALED(retval) || !WIFEXITED(retval), EINVAL, 
            "\"%s\" quits by signal %d.", 
            opt__get_string(OPT__MERGE_PRG),
            WTERMSIG(retval));

    if (WEXITSTATUS(retval) == 0)
    {
        DEBUGP("Remove temporary files.");

        /* Ok, merge done. Remove temporary files, or at least try to. */
        if (unlink(file1) == -1) status=errno;
        if (unlink(file2) == -1) status=errno;
        if (unlink(common) == -1) status=errno;
        STOPIF(status, "Removing one or more temporary files "
                "(merge of \"%s\") failed", output);
    }
    else
    {
        DEBUGP("non-zero return");
        STOPIF_CODE_ERR( WEXITSTATUS(retval) != 1, EINVAL,
                "\"%s\" exited with error code %d",
                opt__get_string(OPT__MERGE_PRG),
                WEXITSTATUS(retval));

        STOPIF( res__mark_conflict(sts, 
                    file1, file2, common, NULL), NULL);

        /* Means merge conflicts, but no error. */
    }

    /* As we've just changed the text, set the current mtime. */
    sts->st.mtim.tv_sec=time(NULL);
    /* Now set owner, group, and mode.
     * This does a lstat(), to get the current ctime and so on;
     * to make the changes visible, we use the meta-data of the target. */
    STOPIF( up__set_meta_data(sts, NULL), NULL);
    sts->st=stat;


ex:
    return status;
}


int rev__get_props(struct estat *sts, 
        char *utf8_path,
        svn_revnum_t revision,
        apr_pool_t *pool)
{
    int status;
    svn_error_t *status_svn;
    apr_hash_t *props;
    char *filename;


    if (!utf8_path)
    {
        STOPIF( ops__build_path(&filename, sts), NULL);
        STOPIF( hlp__local2utf8(filename+2, &utf8_path, -1), NULL);
    }

    STOPIF_SVNERR( svn_ra_get_file,
            (current_url->session,
             utf8_path,
             revision,
             NULL, 
             NULL,
             &props,
             pool) );
    STOPIF( prp__set_from_aprhash(sts, props, STORE_IN_FS, NULL, pool), NULL);

ex:
    return status;
}


int rev___handle_dir_mtime(struct estat *dir,
        enum rev___dir_change_flag_e dir_flag)
{
    int status;
    char *path;


    /* Now, after all has been said and done for the children, set and re-get 
     * the actual meta-data - the mtime has been changed in the meantime 
     * (because of child node creation), and maybe this filesystem's 
     * granularity is worse than on commit; then the timestamps would be 
     * wrong. */
    status=0;
    DEBUGP("dir_flag says %X", dir_flag);


    if (dir_flag & SET_CURRENT) goto a;
    if (dir_flag & REVERT_MTIME) goto b;
    if (dir->remote_status & FS_META_CHANGED) goto c;
    if (dir_flag & GET_TSTAMP) goto d;
    /* Is there some better syntax? Some kind of switch with 
     * case-expressions?
     *
     * I had a lot of if () { } with partially-overlapping conditions:
     *   if (dir->flag &  x) A();
     *   if (dir->flag & (x|y)) B();
     * but gcc wouldn't simply emit a "jmp" to B() after the A() - and I 
     * couldn't easily see that the statements were accumulative.
     * */
    goto x;

a: 
    /* If there's an intentional change (like merging), the current time is 
     * taken. */
    time( & dir->st.mtim.tv_sec );
b:
    /* Make sure that the value is written back to the filesystem.*/
    dir->remote_status |= FS_META_MTIME;
c:
    STOPIF( up__set_meta_data(dir, NULL), NULL);
d:
    /* ops__update_single_entry() would trash the entry_status field! */
  STOPIF( ops__build_path(&path, dir), NULL);
    STOPIF( hlp__lstat(path, &dir->st), NULL);

    /* If it had changes, we'll have to check next time. */
    if (dir->entry_status & FS_CHANGED)
        dir->flags |= RF_CHECK;

x:

ex:
    return status;
}


int rev___revert_to_base(struct estat *sts,
        enum rev___dir_change_flag_e *dir_change_flag,
        apr_pool_t *pool)
{
    int status;
    svn_revnum_t wanted;
    struct estat copy;
    char *path;


    status=0;
    STOPIF( ops__build_path(&path, sts), NULL);

    /* Garbage collection for entries that should be ignored happens in 
     * waa__output_tree(); changing the tree while it's being traversed is 
     * a bit nasty. */

    if ( (sts->flags & RF_UNVERSION))
    {
        /* Was marked as to-be-unversioned? Just keep it. */
        sts->flags &= ~RF_UNVERSION;
        DEBUGP("removing unversion on %s", path);
    }
    else if ( sts->flags & RF_ADD )
    {
        /* Added entry just gets un-added ... ie. unknown. */
        sts->to_be_ignored=1;
        DEBUGP("removing add-flag on %s", path);
    }
    else if (!( (sts->flags & (RF_COPY_BASE | RF_COPY_SUB)) || sts->url ) )
    {
        /* We have no URL, and no copyfrom source ... this is an unknown entry.
         * Has to be given directly on the command line, but could have happened 
         * via a wildcard - so don't stop working.
         * Can't do anything about it. */
        printf("Cannot revert unknown entry \"%s\".\n", path);
        status=0;
        goto ex;
    }
    else
    {
        /* We know where to get that from. */
        DEBUGP("have an URL for %s", path);

        if ( sts->flags & RF_CONFLICT )
        {
            *dir_change_flag |= REVERT_MTIME;
            STOPIF( res__remove_aux_files(sts), NULL);
        }

        /* If not seen as changed, but target is BASE, we don't need to do 
         * anything. */
        if (!opt_target_revisions_given &&
                !(sts->entry_status & FS__CHANGE_MASK))
            goto ex;


        wanted=opt_target_revisions_given ? opt_target_revision : sts->repos_rev;
        /* The base directory has no revision, and so can't have a meaningful 
         * value printed. */
        /* In case we're doing a revert which concernes multiple URLs, they might 
         * have different BASE revisions.
         * Print the current revision. */


        if (sts->parent && (!number_reverted || last_rev != wanted))
        {
            if (opt__get_int(OPT__VERBOSE) > VERBOSITY_VERYQUIET)
                printf("Reverting to revision %s:\n", hlp__rev_to_string(wanted));
            last_rev=wanted;
        }
        number_reverted++;


        /* see below */
        copy=*sts;

        DEBUGP("l_st=%s, r_st=%s, old=%p", 
                st__status_string_fromint(sts->entry_status), 
                st__status_string_fromint(sts->remote_status), 
                sts->old);

        /* Parent directories might just have been created. */
        if (!S_ISDIR(sts->st.mode))
        {
            DEBUGP("file was changed, reverting");

            /* \todo It would be nice if we could solve meta-data *for the current 
             * revision* only changes without going to the repository - after all, 
             * we know the old values.
             * \todo Maybe we'd need some kind of parameter, --meta-only? Keep 
             * data, reset rights.
             * */
            /* TODO - opt_target_revision ? */
            STOPIF( rev__install_file(sts, wanted, sts->decoder, pool),
                    "Unable to revert entry '%s'", path);
            *dir_change_flag |= REVERT_MTIME;
        }
        else
        {
#if 0
            if (sts->entry_status & FS_NEW)
                conflict();
#endif
            if (sts->entry_status & FS_REMOVED)
            {
//              sts->st.mode ist 040755 (file); old ist NULL.
                status = (mkdir(path, sts->st.mode & 07777) == -1) ? errno : 0;
                if (status == EEXIST)
                {
                DEBUGP("old=%p", sts->old);
                }
                DEBUGP("mkdir(%s) says %d", path, status);
                STOPIF(status, "Cannot create directory '%s'", path);
                *dir_change_flag |= REVERT_MTIME;

                /* As we just created the directory, we need *all* meta-data reset.  
                 * */
                sts->remote_status |= FS_META_CHANGED;
            }
            else
            {
                /* Code for directories.
                 * As the children are handled by the recursive options and by \a 
                 * ops__set_to_handle_bits(), we only have to restore the directories' 
                 * meta-data here. */
                /* up__set_meta_data() checks remote_status, while we here have 
                 * entry_status set. */
                sts->remote_status=sts->entry_status;
            }

            STOPIF( up__set_meta_data(sts, NULL), NULL);
            if (sts->entry_status)
                sts->flags |= RF_CHECK;
        }
    }

    /* There's no change anymore, we're at BASE.
     * But just printing "...." makes no sense ... show the old status. */
    sts->flags |= RF_PRINT;

ex:
    return status;
}


int rev___no_local_change(struct estat *sts)
{
  sts->entry_status=0;
    return st__progress(sts);
}


int rev___local_revert(struct estat *dir, 
        apr_pool_t *pool)
{
    int status;
    int i, do_undo;
    struct estat *sts;
    apr_pool_t *subpool;
    enum rev___dir_change_flag_e dir_flag;


    status=0;
    subpool=NULL;
    dir_flag= NOT_CHANGED;

    for(i=0; i<dir->entry_count; i++)
    {
        sts=dir->by_inode[i];
        STOPIF( apr_pool_create(&subpool, pool), "Cannot get a subpool");

        do_undo = sts->do_this_entry && 
            (sts->entry_status & FS__CHANGE_MASK) &&
            ops__allowed_by_filter(sts);

        DEBUGP("on %s: do_undo=%d, st=%s", sts->name, do_undo,
                st__status_string_fromint(sts->entry_status));

        if (do_undo)
            STOPIF( rev___revert_to_base(sts, &dir_flag, subpool), NULL);

        if (S_ISDIR(sts->st.mode) && 
                (sts->entry_status & FS_CHILD_CHANGED))
            STOPIF( rev___local_revert(sts, subpool), NULL);
    
        if (do_undo)
            STOPIF( st__status(sts), NULL);


        apr_pool_destroy(subpool);
        subpool=NULL;
    }

    /* We cannot free the memory earlier - the data is needed for the status 
     * output and recursion. */
    STOPIF( ops__free_marked(dir, 0), NULL);

    /* The root entry would not be printed; do that here. */
    if (!dir->parent)
        STOPIF( st__status(dir), NULL);


    STOPIF( rev___handle_dir_mtime(dir, dir_flag), NULL);

ex:
    return status;
}


int rev__work(struct estat *root, int argc, char *argv[])
{
    int status;
    char **normalized;
    time_t delay_start;
    svn_revnum_t rev;


    status=0;
    /* For revert the default is non-recursive. */
    opt_recursive--;

    if (!argc) ac__Usage_this();

    STOPIF( waa__find_common_base(argc, argv, &normalized), NULL);

    STOPIF( url__load_nonempty_list(NULL, 0), NULL);

    if (opt_target_revisions_given)
    {
        STOPIF( wa__warn( WRN__MIXED_REV_WC, EINVAL,
                    "Sorry, fsvs currently doesn't allow mixed revision working copies.\n"
                    "Entries will still be compared against the BASE revision.\n"),
                NULL);

        // TODO: necessary?
        action->local_callback=rev___no_local_change;
    }
    else
    {
        /* No revision given - just go back to BASE. */
        action->local_callback=st__progress;
    }


    /* This message can be seen because waa__find_common_base() looks for
     * an "url" file and not for a "dir" -- which means that this tree
     * was never committed, so we don't know what HEAD is. */
    /* Maybe the user could still try with some revision number and we simply
     * check for the existence of the given path there? */
    status=waa__read_or_build_tree(root, argc, normalized, argv, NULL, 1);
    if (status == -ENOENT)
        STOPIF(status,
                "!We know nothing about previous or current versions, as this tree\n"
                "was never checked in.\n"
                "If you need such an entry reverted, you could either write the needed\n"
                "patch (and send it to dev@fsvs.tigris.org), or try with a 'sync-repos'\n"
                "command before (if you know a good revision number)\n");
    else
        STOPIF(status, NULL);

    STOPIF( st__progress_uninit(), NULL);


    if (opt_target_revisions_given)
    {
        while ( ! ( status=url__iterator(&rev) ) )
        {
            STOPIF( cb__record_changes(root, rev, current_url->pool), NULL);
        }
        STOPIF_CODE_ERR( status != EOF, status, NULL);

        STOPIF( rev__do_changed(root, global_pool), NULL);
    }
    else
    {
        /* The local changes are taken as to be undone.
         *
         * We cannot go by estat::entry_status - things like RF_ADD have to be 
         * undone, too.
         *
         * waa__do_sorted_tree() can't be used, either, because it does the 
         * directory *before* the children - which makes the directories' mtime 
         * wrong if children get created or deleted. */
        STOPIF( rev___local_revert(root, global_pool), NULL);
    }

    
    /* If this was a revert with destination revision, we might have changed 
     * the entire hierarchy - replaced directories with files, etc.
     * This changed tree must not be written, because it's not the state of 
     * BASE.
     *   [ And if we had to write the original (BASE) list for some cause,
     *     we'd have to read the list afresh, and change what we have to.
     *     Or, the other way: when getting the changes for the given revision 
     *     from the repository we'd have to put them in the estat::old shadow 
     *     tree, to keep the entry list correct. ]
     *
     * If this was a revert to BASE, we have to write the list, because the 
     * ctime of the inodes will be changed - and would mark the entries as 
     * "maybe changed". */
    if (!opt_target_revisions_given)
    {
        delay_start=time(NULL);
        STOPIF( waa__output_tree(root), NULL);
        STOPIF( hlp__delay(delay_start, DELAY_REVERT), NULL);
    }

ex:
    return status;
}


int rev___undo_change(struct estat *sts, 
        enum rev___dir_change_flag_e *dir_change_flag,
        apr_pool_t *pool)
{
    int status;
    char *fn;
    const char *unique_name_mine, 
                *unique_name_remote, 
                *unique_name_common;
    char revnum[12];
    int j;
    struct estat *removed;
    struct sstat_t st;


    STOPIF( ops__build_path( &fn, sts), NULL);
    DEBUGP_dump_estat(sts);

    /* If we remove an entry, the entry_count gets decremented; 
     * we have to repeat the loop *for the same index*. */


    unique_name_mine=NULL;

    /* Conflict handling; depends whether it has changed locally. */
    if (sts->entry_status & FS_CHANGED)
        switch (opt__get_int(OPT__CONFLICT))
        {
            case CONFLICT_STOP:
                STOPIF( EBUSY, "!The entry %s has changed locally", fn);
                break;

            case CONFLICT_LOCAL:
                /* Next one, please. */
                STOPIF_CODE_EPIPE( printf("Conflict for %s skipped.\n", fn), NULL);
                goto ex;

            case CONFLICT_REMOTE:
                /* Just ignore local changes. */
                break;

            case CONFLICT_MERGE:
            case CONFLICT_BOTH:
                /* Rename local file to something like .mine. */
                STOPIF( hlp__rename_to_unique(fn, ".mine", 
                            &unique_name_mine, pool), NULL);
                /* Now the local name is not used ... so get the file. */
                break;

            default:
                BUG("unknown conflict resolution");
        }


    /* If the entry has been removed in the repository, we remove it
     * locally, too (if it wasn't changed).
     * But the type in the repository may be another than the local one -
     * so we have to check what we currently have. */
    /* An entry can be given as removed, and in the same step be created
     * again - possibly as another type. */

    /* If the entry wasn't replaced, but only removed, there's no sts->old. 
     * */
    removed=sts->old ? sts->old : sts;
    if (removed->remote_status & FS_REMOVED)
    {
        /* Is the entry already removed? */
        /* If there's a typechange involved, the old entry has been 
         * renamed, and so doesn't exist in the filesystem anymore. */
        if ((sts->entry_status & FS_REPLACED) != FS_REMOVED &&
                !unique_name_mine)
        {
            /* Find type. Small race condition - it might be removed now. */
            if (TEST_PACKED(S_ISDIR, removed->old_rev_mode_packed))
            {
                STOPIF( up__rmdir(removed, sts->url), NULL);
            }
            else
                STOPIF( up__unlink(removed, fn), NULL);
        }

        *dir_change_flag|=REVERT_MTIME;
    }


    /* Is there some kind of garbage that has to be removed? */
    if (TEST_PACKED(S_ISGARBAGE, sts->local_mode_packed))
    {
        DEBUGP("cleaning garbage");
        STOPIF_CODE_ERR( unlink(fn) == -1, errno,
                "Cannot remove garbage entry %s", fn);
    }



    /* If we change something in this directory, we have to re-sort the 
     * entries by inode again. */
    sts->parent->to_be_sorted=1;

    if ((sts->remote_status & FS_REPLACED) == FS_REMOVED)
    {
        sts->to_be_ignored=1;
        goto ex;
    }
    current_url=sts->url;

    if (S_ISDIR(sts->st.mode))
    {
        *dir_change_flag|=REVERT_MTIME;
        STOPIF( waa__mkdir_mask(fn, 1, sts->st.mode), NULL);

        /* Meta-data is done later. */

        /* An empty directory need not be sorted; if we get entries,
         * we'll mark it with \c to_be_sorted .*/
    }
    else if (sts->remote_status & (FS_CHANGED | FS_REPLACED))
        /* Not a directory */
    {
        STOPIF( rev__install_file(sts, 0, sts->decoder, pool), NULL);
        *dir_change_flag|=REVERT_MTIME;

        /* We had a conflict; rename the file fetched from the 
         * repository to a unique name. */
        if (unique_name_mine)
        {
            *dir_change_flag|=SET_CURRENT;

            /* If that revision number overflows, we've got bigger problems.  
             * */
            snprintf(revnum, sizeof(revnum)-1, 
                    ".r%llu", (t_ull)sts->repos_rev);
            revnum[sizeof(revnum)-1]=0;

            STOPIF( hlp__rename_to_unique(fn, revnum,
                        &unique_name_remote, pool), NULL);

            /* If we're updating and already have a conflict, we don't 
             * merge again. */
            if (sts->flags & RF_CONFLICT)
            {
                STOPIF_CODE_EPIPE(
                        printf("\"%s\" already marked as conflict.\n", fn), 
                        NULL);
                STOPIF( res__mark_conflict(sts, 
                            unique_name_mine, unique_name_remote, NULL), NULL);
            }
            else if (opt__get_int(OPT__CONFLICT) == CONFLICT_BOTH)
            {
                STOPIF( res__mark_conflict(sts, 
                            unique_name_mine, unique_name_remote, NULL), NULL);

                /* Create an empty file,
                 * a) to remind the user, and
                 * b) to avoid a "Deleted" status. */
                j=creat(fn, 0777);
                if (j != -1) j=close(j);

                STOPIF_CODE_ERR(j == -1, errno, 
                        "Error creating \"%s\"", fn);

                /* up__set_meta_data() does an lstat(), but we want the 
                 * original values. */
                st=sts->st;
                STOPIF( up__set_meta_data(sts, fn), NULL);
                sts->st=st;
            }
            else if (opt__get_int(OPT__CONFLICT) == CONFLICT_MERGE)
            {
                STOPIF( rev__install_file(sts, sts->old_rev, 
                            NULL, pool), NULL);

                snprintf(revnum, sizeof(revnum)-1, 
                        ".r%llu", (t_ull)sts->old_rev);
                revnum[sizeof(revnum)-1]=0;

                STOPIF( hlp__rename_to_unique(fn, revnum,
                            &unique_name_common, pool), NULL);

                STOPIF( rev__merge(sts, 
                            unique_name_mine, 
                            unique_name_common, 
                            unique_name_remote), NULL);
            }
            else
                BUG("why a conflict?");
        }
    }
    else 
    {
        /* If user-defined properties have changed, we have to fetch them 
         * from the repository, as we don't store them in RAM (due to the  
         * amount of memory possibly needed). */
        if (sts->remote_status & FS_PROPERTIES)
            STOPIF( rev__get_props(sts, NULL, sts->repos_rev, pool), NULL);

        if (sts->remote_status & FS_META_CHANGED)
        {
            /* If we removed the file, it has no meta-data any more;
             * if we fetched it via rev__get_file(), it has it set already.
             * Only the case of *only* meta-data-change is to be done. */
            STOPIF( up__set_meta_data(sts, fn), NULL);
        }
    }


ex:
    return status;
}


int rev__do_changed(struct estat *dir, 
        apr_pool_t *pool)
{
    int status;
    int i;
    struct estat *sts;
    apr_pool_t *subpool;
    enum rev___dir_change_flag_e dir_flag;


    status=0;
    subpool=NULL;
    dir_flag= (dir->entry_status & FS_NEW) || 
        (dir->remote_status & FS_NEW) ? REVERT_MTIME : NOT_CHANGED;

    /* If some children have changed, do a full run.
     * Else just repair meta-data. */
    if (!(dir->remote_status & FS_CHILD_CHANGED))
        DEBUGP("%s: no children changed", dir->name);
    else for(i=0; i<dir->entry_count; i++)
    {
        sts=dir->by_inode[i];

        STOPIF( apr_pool_create(&subpool, pool), "Cannot get a subpool");

        if (sts->remote_status & FS__CHANGE_MASK)
            STOPIF( rev___undo_change(sts, &dir_flag, subpool), NULL);

        /* We always recurse now, even if the directory has no children.
         * Else we'd have to check for children in a few places above, which would
         * make the code unreadable. */
        if (S_ISDIR(sts->st.mode) &&
                (sts->remote_status & FS_REPLACED) != FS_REMOVED)
        {
            apr_pool_destroy(subpool);
            subpool=NULL;
            STOPIF( apr_pool_create(&subpool, pool), "subpool creation");

            STOPIF( rev__do_changed(sts, subpool), NULL);
        }   

        STOPIF( st__rm_status(sts), NULL);

        apr_pool_destroy(subpool);
        subpool=NULL;
    }

    /* We cannot free the memory earlier - the data is needed for the status 
     * output and recursion. */
    STOPIF( ops__free_marked(dir, 0), NULL);

    /* The root entry would not be printed; do that here. */
    if (!dir->parent)
        STOPIF( st__rm_status(dir), NULL);

    /* If the directory had local modifications, we need to check it 
     * next time -- as we take its current timestamp,
     * we'd miss the new or deleted entries. 
     * Must be done before \c ops__update_single_entry() - That sets 
     * \c dir->entry_status .*/
    if (dir->entry_status & FS__CHANGE_MASK)
        dir->flags |= RF_CHECK;

    STOPIF( rev___handle_dir_mtime(dir, dir_flag), NULL);


ex:
    return status;
}

---